On the Malleus of the Lacertilia, and the Malar and Quadrate Bones of Mammalia

Before passing to the consideration of my own observations I will briefly review the state of the question. This cannot be better accomplished than by reproducing the excellent recapitulative tables given by M. Albrecht.

From the contents of these, tables it follows:

1st. That according to the anatomists who have preceded M. Albrecht, the lower gnathostomous Vertebrata have their jaws hinged by means of a quadrato-articular articulation; whilst Mammalia are provided with an entirely different kind of articulation, concerning the exact nature of which these anatomists are at variance.

2nd. That according to the same authors the Promammalia² must have possessed originally a quadrato-articular articulation of the lower jaw, but that they have lost it (Huxley, Parker, and Bettany), or at least have given up its use in the act of mastication (Gegenbaur and von Kölliker), and that at the same time their quadrate (Huxley, Parker, and Bettany), and perhaps also the articular (Gegenbaur and von Kölliker) and angular elements (von Kölliker) of their mandible have become included in the chain of the ossicula auditus.

After this statement M. Albrecht³ continues:

1st. That he is persuaded that all of the ossicula auditus of Mammalia are represented by homologues in the Amphibia, and by all the ossicula auditus of the Sauropsida, and that they correspond to the suspensorium of fish. The facts may be stated as follows:

Thus, since the quadrate does not form any part at all of the interfenestral chain of Sauropsida, it cannot enter into the composition of that of Mammalia.

2nd. That it is not possible to understand (especially on the theory of Gegenbaur, v. Kolliker, and others) how the Mammalia could have acquired an articulation of the lower jaw different from that of other gnathostomous Vertebrata, and that, therefore, he is of opinion that the glenoid cavity of Mammalia ought still to be found in the quadrate bone.

M. Albrecht has in his hands at the present time the skull of a new-born child, in which the squamous portion of the temporal bone is divided into two parts, viz.:

• α.

  The squamous portion of the temporal bone, properly so called, the homologue, in his opinion, of the squamosal of Sauropsida.

• β.

  The zygomatic portion bearing the glenoid cavity, and thus homologous, with the quadratum of the Sauropsida.

Other cases of the complete separation of the squamosal and the quadrate are mentioned in literature, and are cited by M. Albrecht. In addition this distinguished anatomist states that he has observed traces of a squamoso-quadratic suture in several skulls of apes in the Royal Belgian Museum of Natural History, and that he will shortly publish an account of them.

To sum up, M. Albrecht’s arguments lead, on the whole, to the following two conclusions:

1st. The quadrate cannot form part of the interfenestral chain of bones of Mammalia.

2nd. One of the two bones (the zygomatic portion) formed by the division of the so-called squamosal is doubtless the homologue of the quadrate of Sauropsida.

I shall examine these two statements successively, in order to show whether the results of my own observations tend to confirm or invalidate M. Albrecht’s conclusions.

Can the quadrate form a part of the interfenestral chain?

It is evident that if there were found simultaneously existing in the same animal a mandible composed of six normal elements, a true quadrate, and a malleus, it would immediately follow that it was impossible that that quadrate could form any part of the chain of ossicula auditus, for—

1st. It could not be confounded with the malleus, because there would already be one there.

2nd. It would be still more impossible to identify it with the remainder of the interfenestral chain, because it would be situated outside the malleus, and would not touch any of the remaining ossicula.

Everything depends, therefore, on the discovery of a malleus in the condition described above. Now, I have found in several Lacertilia (Leiolepis guttatus, Ctenosaura pectinata, Uromastix spinipes, Lophyrus dilophus, Basiliscus vittatus) a small bone which appears to answer the question. I shall endeavour to prove that it has really the morphological value of a malleus.

• α.

  Firstly, it has the form of a malleus; it being possible to distinguish in it:

  • A capitulum.

  • A cervix.

  • A manubrium.

  • A processus gracilis.

• β.

  It has the same connections; that is to say:

  • It is applied along the tympanic membrane in such a manner that the manubrium is parallel to the membrane.

  • It is united besides to the remainder of the interfenestral chain by means of a cartilage attached to it in the region of the cervix.

  • It lies in contact with the quadrate in exactly the same manner as that in which the malleus of Mammalia is in contact with the quadrate of M. Albrecht.

• γ.

  It is connected with the articular element of the mandible by means of a malleo-articular ligament, which M. Albrecht identifies with the extra-mandibular portion of Meckel’s cartilage.

• δ.

  There is little doubt, there appears to me, that this malleus is identical with that described by Peters as existing in the crocodile,¹ and with the “suprastapedial extrastapedial (manubrium) “of Mr. W. K. Parker.²

  This being admitted, the first of the naturalists cited has demonstrated the continuity of the malleus with Meckel’s cartilage, as in Mammalia,³ an observation confirmed by the English naturalist. This result, therefore, is in support of the opinion expressed in δ.

• ε.

  The malleus of Mammals serves for the insertion of a small muscle (tensor tympani), the origin of which is in the otic region of the cranium. The same occurs in the case of the malleus of Lacertilians.⁴

To sum up, then, I believe that I have discovered in Lacertilia a real malleus, the homologue of that of Mammalia, and with that fact as a starting-point it appears that the conclusion may be formed that the quadrate of Mammalia is not to to be sought for amongst their ossicula auditus. In this respect, therefore, M. Albrecht’s theory receives confirmation, although it will be necessary that it should be slightly modified. Instead of the statement with regard to reptiles:¹

Columella = malleus + incus + os lenticulare + stapes, the matter must stand thus:

Columella = incus + os lenticulare + stapes.

Is the quadrate of M. Albrecht really the homologue of the quadrate of Sauropsida ?

Such is the second question to be considered. Before going further it will be well to consider what are reasons given by M. Albrecht in favour of his interpretation. They are three in number.

1st. The quadrate of Mammalia, since it could not find place in their interfenestral chain, must be to be found elsewhere.

2nd. The glenoid cavity ought still be found in the quadrate bone.

3rd. There are a certain number of instances known in which the squamous portion of the temporal bone of man, or of the primates, is divided into two parts.

• α.

  The squamous bone properly so called.

• β.

  The zygomatic portion.

It appears to me that two further methods of inquiry should be employed to make certain whether the quadrate of M. Albrecht is a real quadrate or not. These are:

1st. The examination of its connections.

2nd. The study of its development.

Leaving aside the latter question, to which M. Albrecht proposes to return shortly, the attempt will be made to demonstrate the correctness of his views by the former method.

Nevertheless, before this interesting subject is commenced, it is indispensable to determine the morphological value of the malar bone of Mammalia, since this determination will be of the greatest utility in the sequel.

In a recent work ¹ M. Albrecht.has proved that the malar bone of Mammalia ought to be considered as formed of three parts, which he calls

By comparison with the Sauropsida M, Albrecht arrives at the following interpretation of these parts:

Premalar—Anterior postfrontal.

Postmalar—Posterior postfrontal.

Hypomalar—Quadrato jugal.

Lastly, in his opinion a small isolated bone discovered in a young Cynocephalus appears to represent the jugal, which is usually co-ossified with the supramaxillary bone.

I regret that I cannot agree with his conclusions, for in fact:

1st. The bone of the Cynocephalus appears to me to be simply a wormian bone, which has appeared at this spot as if for the very purpose of leading to the construction of a theory.

2nd. In M. Albrecht’s comparison, the jugal is excluded from taking part in the contour of the orbit, an arrangement of which I know no other example, not even in the Lacertilians with the double postfrontal.

3rd. Why should it be desired to assign to the human subject two postfrontals, when in the Sauropsida this structure is only to be met with amongst the Lacertilia, and even amongst these an exception rather than the rule ?

(Continued on page 592.)

(Notes to the tabular statement on page 590.)

¹ I observe the following arrangement in Rhynchosuclius Schlegelii:

This fact will be made use of in a moment.

² Cuvier, ‘Ossemens fossiles,’ 1836, pl. 239, figs. 9—12.

³ Cuvier, loc. cit., figs. 17—20.

⁴ A. Milne-Edwards, “Mémoire sur le type d’une nouvelle famille de l’ordre des Ronguers,” ‘Nouvelles Archives du Museum de Paris,’ 1867, p. 66 and pl. vii, figs. 1, 2, 3, 4.

⁵ The formula, as well as the preceding one, assumes that the quadrate of M. Albrecht is really a quadrate. Otherwise we have:

that is to say, the structure of a Chelonian, in which the supra-temporal fossa has remained open, and in which the quadrate has been withdrawn and transformed into an auditory ossicle.

⁶ T. H. Huxley, ‘A Manual, &c.,’ p. 282.

⁷ T. H. Huxley, ‘A Manual, &c.,’ p. 220.

⁸ T. H. Huxley, ‘A Manual, &c.,’ p. 233—238.

⁹ T. H. Huxley, ‘A Manual, &c.,’ p. 230.

¹⁰ T. H. Huxley, ‘A Manual, &c.,’ p. 225.

¹¹ T. H. Huxley, ‘A Manual, &c.,’ p. 228.

¹² T. H. Huxley, ‘A Manual, &c.,’ p. 228.

¹³ Cuvier, loc. cit., figs. 21—34.

4th. M. Albrecht’s ¹ former interpretation, viz. that the jugal when it is not ossified by a particular centre is ossified either by the supra-maxillary or by the quadrato-jugal, appears to me even less capable of defence, for among the living Sauropsida possessing a quadrato-jugal Hatteriais the only one in which this bone is fused to the jugal. In Hatteria we have to deal with an exception. Therefore, why should it be desired to render the condition in the human subject a matter of exception rather than to bring it within the rule ? In other words, it appears to me more rational to assign to Man a separate quadrato-jugal, such as occurs in Birds, Chelonians, and Crocodilia.

The explanation which follows seems to me a more correct one, because by its application all the objections we have just passed in review disappear.

Premalar = Jugal.

Postmalar=Postfrontal.

Hy pom alar=Quadrato-j ugal.

This, if M. Albrecht’s quadrate be admitted, gives us the formula:

Let us attempt to discover in the Sauropsida an analogous arrangement, in order to better justify our theory.

If a skull of Hatteria be examined, it is seen that three temporal fossæ can be distinguished,² a latero-temporal, a supra-temporal, and a post-temporal. I have discussed the variations of the latter at length in another memoir,³ and it is not therefore necessary to return to the subject here. Let us study the variations of the two former; they are comprehended in the table on page 590.

Let us now compare the formula given for man with that of Rhynchosuchus Schlegelii.

Homo sapiens. Rhynchosuclius Schlegelii.

Only two things are necessary to pass from one to the other, viz.:

1st. The disjunction of the squamoso-postfrontal arch.

2nd. The closing together of all the other bones under consideration.

Now, the former condition is very common amongst the Sauropsida. It is to be observed, as has been already stated, in the Ophidians, the Amphisbœnidæ, the Ascalobotidæ, the Chalcidea and Ophidiiform Scincoidea, the Chelonia, and in Birds; whilst the latter is by no means rare amongst the Chelonia.

Before resuming the discussion concerning the quadrate, I may again express my opinion, based on the facts which follow, that—

1st. The Lacertilia and Ophidia possessed originally an ossified quadrato-jugal.

2nd. That therefore there existed originally in all the Sauropsida a latero-temporal fossa bounded thus:

My reasons are as follows:

1st. The ancient Reptiles (Ichthyosauria, Plesiosauria, Dinosauria, &c.) possessed an ossified quadrato-jugal

2nd Amongst the existing Sauropsida, Birds, Crocodiles, and Chelonians, as well as Hatteria, possess one still.

3rd. This latter animal represents amongst the Lacertilia a primitive type, as it is closely allied to the Triassic Rhynchosaurus.

4th. The quadrato-jugal exists still in a ligamentous condition in the Ophidia and Lacertilia, and this is certainly an indication of rudimentation since in all the Chalcideæ and ophidiiform Scincoidea the squamoso-postfrontal arch likewise becomes ligamentous

Let us now consider by what peculiarities in its connections the quadrate of Sauropsida is distinguished, and then examine whether these peculiarities are also to be found in M. Albrecht’s quadrate.

The quadrate of Sauropsida may be in relation—

1st. At its proximal extremity with the squamosal, the parietal, and the parotic process (Iguana).

2nd. At its proximal extremity again with the malleus (Uromastix).

3rd. At its distal extremity with the mandible and the pterygoids (Iguana).

4th. At its distal extremity again with the quadrato-jugal (Crocodile).

5th. Occasionally with the postfrontal (Rhynchosuchus).

6th. Lastly, with the tympanic membrane, which is inserted into it in a posteriorly placed concavity, which might be termed the tympanic concavity (Iguana).

Now, all these relations, excepting the one with the pterygoid, occur in the case of M. Albrecht’s quadrate. If, then, it is borne in mind that it is solely because of the enormous development (compared to that in the Sauropsida) of the alisphenoid in man that the separation of the quadrate and pterygoid is due, it will be admitted that M. Albrecht had good grounds for holding the quadrate of the lower gnathostomous Vertébrala as homologous with the zygomatic portion of the squamous part of the temporal bone of Mammalia.

To resume:

I. I believe that I have discovered in Lacertilia a true malleus homologous with that of Mammalia, and that this circumstance allows of a modification of the table of homologies given by M. Albrecht¹ in the following manner.

This may be expressed in the following formula:

relations which are to found amongst the Sauropsida also.

III. Lastly, I have by the study of the connections of the bones materially strengthened M. Albrecht’s theory, which holds that the zygomatic portion of the squamous part of the the temporal bone of Mammalia is the homologue of the quadrate of the lower gnathostomous Vertebrata.

In conclusion, it is my duty, which is very agreable to me, to thank my learned friend, Professor P. Albrecht, for the liberality with which he has placed at my disposal the wood blocks which he has used in the illustration of his two recent memoirs, and all the more so because they are to be used to attack one of the theories of the distinguished anatomist himself.