60 GENERAL ANATOMICAL CHARACTER 



" agminated " glands ; the latter being more commonly known by the 

 name of "Peyer's patches." These were formerly supposed to be 

 secretory organs, which discharged some kind of fluid into the 

 intestine, but are now more generally considered to belong to that 

 group of structures of somewhat mysterious function of which the 

 lymphatic and lacteal glands are members. The solitary glands are 

 found scattered irregularly throughout the whole intestinal tract ; 

 the agminated, on the other hand, are always confined to the small 

 intestine, and are most abundant in its lower part. They are 

 subject to great variation in number and in size, and even 

 in different individuals of the same species, and also differ in 

 character at different periods of life, becoming atrophied in old 



age. 



Liver. — The distinct glands situated outside the walls of the 

 intestinal canal, but which pour their secretion into it, are the 

 pancreas and the liver. The latter is the more important on 

 account of its size, if not on account of the direct action of its 

 secretion in the digestive process. This large gland, so complex in 

 structure and function, is well developed in all mammals, and its 

 secreting tube, the bile-duct, always opens into the duodenum, or 

 that portion of the canal which immediately succeeds the stomach. 

 It is situated on the riskt side of the abdomen in contact with the 

 diaphragm and the stomach, but varies greatly in relative size, and 

 also in form, in different groups of mammals. In most mammals a 

 gall-bladder, consisting of a pyriform diverticulum from the bile- 

 duct, is present, but in many this appendage is wanting, and it is 

 difficult to find the rationale of its presence or absence in relation 

 to use or any other circumstance in the animal economy. 



The descriptions of the livers of various animals to be met 

 with in treatises or memoirs on comparative anatomy are very 

 difficult to understand for want of a uniform system of nomencla- 

 ture. The difficulty usually met with arises from the circumstance 

 that this organ is divided sometimes, as in Man, Ruminants, and 

 the Cetacea, into two main lobes, which have been always called 

 respectively right and left, and in other cases, as in the lower 

 Monkeys, Carnivora, Insectivora, and several other orders, into a 

 larger number of lobes. Among the latter the primary division usu- 

 ally appears at first sight tripartite, the whole organ consisting of a 

 middle, called " cystic " or " suspensory " lobe, and two lateral lobes, 

 called respectively right and left lobes. This introduces confusion 

 in describing livers by the same terms throughout the whole series 

 of mammals, since the right and left lobes of the Monkey or Dog, 

 for instance, do not correspond Avith parts designated by the same 

 names in Man and the Sheep. There are, moreover, conditions 

 where neither the bipartite nor the tripartite system of nomencla- 

 ture will answer, so that we should have considerable difficulty in 



