THE PANCREAS. 113 



the suspensory ligament. That which unites it to the ventral wall. of the stomach and duo- 

 denum also becomes thinned out ; it forms the small or gastro-hepatic omentum. The liver is 

 at first an exactly symmetrical organ, the right and left lobes being equal in size and 

 symmetrically placed. After the fourth month the right lobe begins relatively to increase in 

 size, and at birth the proportion of this to the left lobe is as 1'6 to 1. The liver also at first 

 grows very rapidly, so that by the second month it nearly fills the abdomen, and causes a 

 well marked prominence on the ventral aspect of the embryo. At this time it is calculated to 

 constitute nearly one half the weight of the body. The proportion, however, gradually 

 decreases, until at term the relative weight of the liver to the whole body is as 1 to 18. The 

 further changes which the blood-vessels which pass to the liver undergo will be considered 

 with the development of the venous system. 



The pancreas is developed as a hollow hypoblastic diverticulum from the dorsal 

 wall of the duodenum opposite the hepatic diverticula, and somewhat later than these 

 (fig. 125, B, C, D,p). This hollow process grows into the mesogastrium or gastro- 

 duodenal mesentery, which: at this time is well developed, and ramifies within this, 

 producing by its off-shoots the ducts and alveoli as with other compound acinous 

 glands. As the duodenal loop becomes formed, and this and the pyloric end of the 

 stomach are turned over towards the right side, the pancreas loses its median sym- 

 metrical position, and with the mesentery which encloses it now lies across the back 

 of the abdomen. This is the condition in which the gland is found in most mammals. 

 But in man, with the fusion of the mesogastrium (great omentum) to the transverse 

 mesocolon, the posterior layer of the mesenteric fold which encloses the pancreas 

 becomes absorbed (Toldt), and the gland becomes fixed across the back of the 

 abdomen, and is now apparently altogether behind the peritoneum (see fig. 12, 129). 



RECENT LITERATURE. 



Bemmelen, J. F. van, Entwikkeling en metamorphose der kieuw of viceral-spalten en der aorta- 

 bogen bij embryonen van Tropidonotus natrix en Lacerta muralis, Kin. Akad. v. Wet. Amsterd. Afd. 

 Natuusk., 1885 ; Die Visceraltaschen u. Aortenbogen bei Reptilien u. Vogeln, Zool. Anzeiger, 1886 ; 

 Die Halsgegend der Reptilien, Zool. Anz., 1887. 



Bonnet, B., Ueber die Entwicklung der Allantois und die Bildung des Afters bei den Wieder- 

 kauern und iiber die Bedeutung der Primitivrinne und des Primitirstreifs bei den Embryonen der 

 Sauyethiere, Anat. Anzeiger, 1888. 



Born, G-., Ueber die Derivate der embryonalen Schlundbogcn und Schlundspalten, Archiv f. 

 mikr. Anat., Bd. xxii., 1883. 



Cadiat, Du developpement desfentes et arcs branchiaux chez Vembryon, Journal de 1'anat., &c., 

 1883. 



Chievitz, J. C., Beitrdge zur Entwicklungsjeschichte der Sveicheldriisen, Arch. f. Anat. u. 

 Physiol., Anat. Abtheil., 1885. 



Demon, F., Developpement de la portion sousdiaphragmatique da tube digestif. Lille, 1884. 



Dohrn, A., Die Thyroidea bei Petromyzon, Amphioxus u. Tunicaten, Mitth. aus der zool. 

 Station z. Neapel, 1886. 



Fischelis, Ph., Beitrdge zur Kenntniss der EntwicTclungsgeschichte der Gl. ihyreoidea u. Gl. 

 thymus, Arch. f. mikr. Anat., Bd. xxv., 1885. 



His, W., Ueber den Sinus prcecervicalis und die Thymusanlage, Archiv f. Anat. u.' Physiol., 

 Anat. Abth., 1886 ; Zur Bildung sgeschichte der Lungen beim menschlichen Embryo, Archiv f. Anat. 

 und Physiol., Anat. Abtheilung, 1887; Schlundspalten w. Thymusanlage (Brief an F. Mall), Arch, 

 f. Anat. u. Physiol., Anat. Abth., 1889. 



Kastschenko, N., Das SchicTcsal der embryonalen Schlundspalten bei Sdugethieren, Archiv f. 

 raikrosk. Anat., Bd. xxx., 1887 ; Das Schlundspaltengebiet des Huhnchens, Arch. f. Anat. u. Phys. 

 Anat. Abth., 1887. 



Liiessner, E., Ein Beitrag zur Kenntniss der Kiemenspalten und Hirer Anlagen bei amnioten 

 Wirbelthieren, MorphoJog. Jahrbuch, Bd. xiii., 1888. 



Mall, F. P., Entwicklung der Branchialbogen und Spalten des Huhnchens, Arch. f. Anat. u. 

 Physiol., Anat. Abth., 1887 ; The branchial clefts of the dog, with special reference to the origin of 

 the thymus gland, Studies from the Biol. Laboratory of John Hopkins University, iv., 1888. 



Meuron, P. de, Recherches sur le developpement du thymus et de la glande thyrolde, Recueil 

 zool. Suisse, iii., 1886 ; Sur le developpement de I'&sophage, Compt. rend., 1886. 



Minot, Ch. S., Evolution of the Lungs, Proceed, of the Zoolog. Society of London, 1886. 



Ostronmoff, A., Ueber den Blastoporus u. d. Schwanzdarm bei Eidechsen u. Sclachiern, Zool. 

 Anzeiger, 1889. 



Philip, R. "W., Beitrdge zur Lehre iiber die Entwicklung cfer Trachea, Mitth. aus d. embryol. 

 Inst. d. Cnivers. Wien, Bd, ii., 1883. 



VOL. I. I 



