608 ORGANS OF SECRETION. 



gelatinous and pellucid, more firm, opaque, red and vascular, 

 and the biliary and pancreatic ducts, originally separate, 

 coalesce by the drawing out of the intervening portion of 

 intestine during development. 



The pancreas opens by a single duct, sometimes into the 

 ductus choledochus, and sometimes separately into the duo- 

 denum, although the division of this organ into two lobes is 

 perceptible in most of the mammalia ; these lobes consist of 

 smaller aggregated lobules or clusters of ramified tubular 

 coeca, ending in vesicular enlargements like the salivary 

 follicles ; and the organ commences its development, like the 

 liver, from a small median coecal protrusion from the fore 

 part of the intestine, which sends out follicles and ramified 

 filiform tubuli through the thickened soft vascular blas- 

 tema. The spleen, in many of the cetacea, is divided, as in 

 many lower vertebrata, into several detached, small, round, 

 portions, connected only by sanguiferous and lymphatic 

 vessels ; it is single and large in the ruminantia, of a regular 

 elongated form, and attached along the side of the paunch. 



The mucous surfaces of mammalia are every where pro- 

 vided with muciparous follicles, presenting the simplest 

 forms of glands, and the alimentary canal has its simple 

 follicular glands of Lieberkuhn andofPeyer; more compli- 

 cated forms of these muciparous organs exist in the labial, 

 buccal, palatine, molar, and amygdaloid glands, the caruncula 

 lachrymalis, and several connected with the urinary and geni- 

 tal apparatus. The serous membranes have also their secret- 

 ing surfaces and bursse, to preserve the mobility of the viscera 

 and joints. The mammary, urinary, and genital glands present 

 numerous modifications in this class ; and the tegumentary or- 

 gans are every where provided with their simple sebaceous folli- 

 cles, and their more complicated sudoriferous and oil glands, as 

 the eyes are furnished with their simple Meibomian and com- 

 plicated lachrymal glands, and the external meatus of the 

 ears with their ceruminous glands. 



From the different habits and external circumstances of 

 the animals of this most varied class, many of the secreting 

 organs are so modified as to appear special developments 

 limited to tribes or to individuals. The most odoriferous 

 parts of the skin of mammalia are sometimes developed into 

 distinct follicles or more complicated glands, as in the inter- 



