ABSTRACT
We have more than once had occasion Quar. Jour, of Micros. Science,’ Nos. IV., V.) to refer to the labours of Dr. Leydig, who has done more than any one, of late years, towards extending our knowledge of histology to the lower Vertebrata and to the Invertebrata.
His essays are characterized not only by the accuracy and elaborateness of their details, but by their breadth of view and the extensive knowledge of Anatomy and Physiology which they indicate. We are acquainted with no more important contributions to the departments of Zoology with which they are concerned than his Memoirs on Lacinularia ; on the larva of Corethra ; on Argulus ; on the anatomy and development of Paludina ; and on the so-called muciparous organs of Fishes, which have appeared in Müller’s Archiv, and in Siebold and Kölliker’s Zeitschrift, in the course of the last five or six years. Of equal value are his ‘ Contributions to the Microscopical Anatomy and Development of the Sharks and Rays,’* published as a small independent work, in 1852 ; followed up in the present year, by that now under notice. Dr. Leydig must be a hard, as well as an able worker ; for his present effort is more considerable than any which have preceded it, and assuredly does not fall below them in scientific value or interest.
It is divided into two sections ; the first of which treats of the histology of the Sturgeon, the second, of that of reptiles in general.
Dr. Leydig’s book requires and deserves careful study, and we must be satisfied with drawing attention to a few of the chief matters of novelty and interest which it contains.
Verifying Ecker’s discovery, that the pituitary body of fishes is a vascular gland, he finds that in the Sturgeon, the pineal gland is of a similar nature, resembling the thyroid, however, rather than the other vascular glands.
As might have been expected, from the zoological position of the Accipenseridae, the ‘ muciferous’ tubes and ampulla of the Sturgeon, are intermediate in structure between the corresponding organs of cartilaginous and osseous fishes.
A new light is thrown upon the nature of the supra-renal capsules by Leydig’s discovery, that in Sturgeons, and other cartilaginous fishes, Batrachia, and Reptilia, they belong to one series of organs with the so-called. ‘ axillary hearts with certain peculiar appendages, discovered by Leydig, upon the ganglion of the sympathetic ; and with the fatty-looking yellow bodies on the blood-vessels and in the kidneys themselves.
In Plagiostomes, in Chimara, and in the Sturgeon, the networks of the hepatic cells lie within canalicular cavities in a kind of connective tissue, by which they are supported. Leydig considers this to be evidence that the liver essentially resembles other glands ; a conclusion to which, however, the evidence he adduces would not lead us.
The author’s investigations into the structure of the spleen of fishes and reptiles are of the highest importance : they fully confirm Remak’s views, and tend to the conclusion that the difference between a spleen, a Peyer’s patch, and a lymphatic gland, is but one of degree ; while they greatly extend our knowledge of the relations between the blood, vascular, and lymphatic systems.
The position and anatomical characters of the Thymus and Thyroid glands are determined for fishes and many reptiles. Histologically they invariably present the same differences as in man.
Leydig doubts the existence of cæcal terminations in the tubuli uriniferi of fishes. His inquiries into the development of the genito-urinary system of Amphibia and reptiles are of the utmost value, and tend to clear up many difficulties in the morphology of these organs, not only in these but in the higher Vertebrata.
Our space prevents us from further analyzing Dr. Leydig’s work ; but we trus twe have said sufficient to justify the high opinion of its merits which we have expressed.
‘ Beiträge zur Mikroskopischen Anatomic und Entwickelungsgeschichte dor Kochen und Haio.’ Leipzig, 1852.
