403 



THE DIGESTIVE APPARATUS IN MAMMALIA. 



The lymphatics constitute three superposed networks in the mucous 

 membrane. The first is situated around the glandular orifices ; it receives 



Fig. 202. 



HORIZONTAL SECTION THROUGH THE MIDDLE PLANE OF THREE PEYERIAN GLANDS, 

 SHOWING THE DISTRIBUTION OF THE BLOOD-VESSELS IN THEIR INTERIOR. 



the central lacteal from each villus; the second is placed between tho 

 glandular and the muscular layer of the mucous 

 Flg * 2( membrane finally, the third exists in the deep 



portion of the membrane, and communicates with 

 the meshes encircling the closed follicles. The 

 most voluminous emergent vessels pass through 

 the wall of the intestine and accompany the blood- 

 vessels between the layers of the mesentery, enter- 

 ing the mesenteric glands, and terminating in the 

 reservoir of Pecquet (receptaculum chyli). 



The nerves are from the solar plexus; they 

 form a submucous reticulation and a myenteric 

 plexus, comprised between the two planes of the 

 muscular tunic. 



Microscopic ganglia are found on their course. 



DEVELOPMENT. The small intestine shows it- 



"'* l? p e Ti in the **". aDd d g 



THE LACTEALS IN A VILLUS. t " e i 03 ** 1 * existence oi Kuminants preserves a very 



, Central lacteal; d, Connec- remarkable predominance over the large intestine : 



tive-tissue corpuscles with a predominance equally marked in the vessels it 



communicating branches ; receives, for, in a foetus of five months, we have 



c,cmated columnar epithe- f oun a the collective arteries of the small intes- 

 8 of which a7e di-~ e equivalent to about ten times the volume of 



- 



rectly contiguous with the tnose ot the caecum and colon. 

 connective tissue corpuscles. FUNCTIONS. It is in this tube, and under the 



