The full citations of different works and memoirs on the subjects of this article render it unnecessary to give any detailed bibliogra phical list at its termination. I may, how ever, call the attention of the reader to the following works already cited, as forming the principal basis of modem knowledge of ovo logy and development, viz.: The Inaugural Dissertation of Pander on the Development of the Chick, published in 1817. The His tory of the Egg before Impregnation, by Pzirkinje, in 1825. The Epistola of Von 33aer, in 1827. The contributions of Von Baer and Rathke to Burdach's Physiology, in 1827 and 1828. The various Memoirs by Rathke at different times, and Von Baer's Lectures on Development, completed in 1837. The Systematic Manual of Develop ment by G. Valentin, in 1835. The Prodro mus and contributions by R. Wagner, in 1836. and the Manual of Physiology by the same author. J. Millie? s Physiology, and especially the English translation of the more recent edition. The researches of _Martin Barry, in 1838 and 1839. The various contributions of Bischoff, beginning in 1838 : His Systematic Treatise on Development in 1842, and his Monographs on the Development of the Rabbit in 1842, of the Dog in 1845, of the Guinea Pig in 1852, and of the Deer in 1855. The researches of Coste beginning in 1833; his work on Comparative Embry-ology in 1837, and his large and beautifully illustrated work, as yet unfinished, beginning in 1850. The works of C. Vogt on the Alytes Obste tricans (Batrachia) and on the Embryology of the Salmonidae, in 1842. Lastly, the re cent and valuable researches of Renzak on the Development of Vertebrata in 1853-1855 ; and the republication of R. Wagner's Icones Physiologicre by Ecker. The works relating to the invertebrate animals are much too numerous for quotation. I will only mention the researches of Kaliker on the Cepha lopoda, of Quatrefages, Vogt, and others on the Mollusca, Annelida, &c., and those of J. Midler on the Echinodermata.
I would also refer the reader to the excel lent report on the progress of discovery in regard to the Ovum by Thon2as W Jones in the Brit. and For. Medical Review for Oct. 1843, to Bischoff's article on the History of Discovery in Development, and its application to the explanation of Malformations in Wag ner's Dictionary of Physiology, to Leuck art's Article on Generation in the same work, and to Vrolik's Memoir on the Explanation of Monstrosity from the History of Deve lopment, and to his article Teratology in this Cyclopmdia. A large amount of information on the whole of our subject will also be found in C. Vogt's interesting Letters on _Living and Fossil Animals in 1851 ; in Victor Carus's Sy stem of Animal Morphology in 1853 ; in Van der Hceven's Manual of Zoo logy, with additions by Leuckart in 1850— 1856 ; and in the English works of Carpenter, Owen, and Rymer Jones on Comparative Anatomy and Physiology.
In now bringing this article to a close, the author owes an apology to the conductors and the readers of this Cyclopmdia for the extreme tardiness with which it has appeared. The delay has arisen, in part, from personal circumstances which need not be mentioned here, and in part from the nature of the sub ject of which the article treats. ln the ori ginal plan of the article, it was intended that it should comprehend, along with the history of the ovum, an account of the development of the embryo. But as time advanced, and every successive year added new and im portant matter to our knowledge of the science, and greatly modified the statement of facts previously regarded as established, it became more and more difficult, especially in the hands of one interested in the experimental investigation of many of the individual facts, to present a systematic and at the same time clear and brief description of the researches of physiologists on the subject of develop ment. The author regrets deeply that he
should thus be prevented from furnishing the readers of the Cyclopmdia with this part of the article as originally intended. But at the same time he believes that when the recent rapid progress of many departments of the subject is considered, and the vast number of details which would be required to embrace even the shortest account of the origin and formation of all the textures and organs of the animal body, the knowledge of which forms a science that is coextensive with the whole range of anatomy and physiology, it may be thought that he has in present cir cumstances judged rightly in abandoning the attempt to compress into a limited space the statement of so extensive and important a branch of physiological inquiry.
(Allen Thomson, M. D.) PANCREA S (114)year*, Gr. ; Pancreas, Lat. ; le Pancreas, Fr.; die Bauchspeicheldriise, Germ. ; Pancrea, Ital.). The pancreas is an azygous, non-symmetrical, glandular organ, possessing a duct, and, therefore, belonging to the category of true glands ; connected anatomically with the alimentary canal, and physiologically with the function of digestion.
On taking even the most superficial and general view of this organ, two or three things cannot to strike the attention : one is, the dose affinity and strong contrariety which it at the same time displays to the salivary glandst —affinity in point of appearance and structure, being, like them, a typical represen tation of a conglomerate gland,—contrariety in point of situation and function, the one being placed at the very threshold of the ali mentary canal, the other at an advanced po sition in it ; the one acting on raw material, and having in part at least a mechanical use I, the other having to do with material far gone in the process of assimilation, and possessing a function, whatever it may be, certainly not mechanical in any degree.
Another striking circumstance is its wide diffusion. It exists in all vertebrata ; — mam malia, birds, reptiles, and most fishes, all possess a pancreas, and that quite independent of what the nature of their food may be, animal, vegetable, or mixed; a fact that one would have imagined would itself have pre vented the adoption of the old views with regard to its function.
Another circumstance, not less striking, is its constant relation to the duodenum : hatever may be the other modifications of the alimentary canal, from the straight and simple tube of some carnivora to the volu minous apparatus of the vegetable feeders, or whatever may be the modified form of the pancreas itself, still, if the organ exists, its relation to the duodenum is invariable ; if there is a duodenal fold, it is placed in it; and if there is not, it makes the closest approxi mation to an analogous position that is pos sible : indeed the uniformity of this relation is so invariable, even under circumstances where it would appear to be indifferent, that one cannot but regard it as one of those in stances of conformity to type in which uni formity appears to exist for uniformity's sake.
The arrangement of the subject of this paper that most naturally suggests itself, is to treat first of the structure, and then of the functions of the organ. I shall therefore arrange my observations under the following .heads :— 1st. The descriptive anatomy of the human pancreas, including an account of so much of its structure as may be rnade out by a naked eye examination.
2nd. Its minute or general anatomy.
3rd. Its comparative anatomy, including those modifications both of the form and ulti mate structure of the gland that the anirnal series exhibits.
4th. The physiology of the pancreas,—the rile that it plays in the function of digestion.
Lastly. A short account of some of the most strikiner pathological changes that the organ is liable to.