472 MANUAL OF HISTOLOGY. 



Passing on to the lymphatic canals of the tonsils (fig. 451) (Frey, Th. 

 Schmidt) we find in the neighbourhood of the capsule and in the latter 

 itself, considerable vessels, with valves and knotty dilatations. From 

 these branches are" given off, internally, some of which encircle, at 

 considerable distance, the bodies of the racemose mucous glands, and 

 some reach the base and external surface of the different divisions 

 of the tonsils. Here they enter into the formation of a network of 

 canals, with greatly dilated nodal points, and some of them penetrate 

 upwards into the tissue connecting the follicles (b). In the latter situa- 

 tion they are remarkable for their extreme fineness and arrangement in 

 dense but irregular networks. Around the follicles themselves (c), these 

 lymphatic canals form circular networks, their calibre being rather 

 small. The interfollicular lymphatics penetrate, to a greater or less 

 distance, towards the surface of the depression which occupies the axial 

 portion of each division of the tonsil, and end here eventually, blind. 



The lymphatics of the lingual crypts possess in all salient points the 

 same arrangement as these just mentioned. 



On account of their near relationship, we will here append a few 

 remarks on the lymphoid organs of the pharynx. The latter, in many 

 mammals, is found to present a very extensive lymphoid infiltration of 

 the mucous membrane. In man, the arch of the pharynx is possessed of 

 follicular glands and a pharyngeal tonsil, composed of a number of the 

 latter. This is situated at the point at which the mucous membrane 

 comes into contact with the base of the skull. It is a mass several lines 

 in thickness, which extends from the opening of one Eustachian tube to 

 the other. In structure it resembles the tonsils. 



The same organ is to be found among the mammalia, as in the pig, 

 sheep, ox, and dog. Other animals, however, are not possessed of it, as, 

 for instance, the hare (Schmidt). 



According to Koelliker, the first rudiments of the tonsils may be seen 

 in the fourth month of intra-uterine life, in the form of a simple depres- 

 sion in the mucous membrane of the mouth. A month later, several 

 other additional little pits are evident, and the lymphoid infiltrated walls 

 are of considerable thickness. The follicles appear subsequently in the 

 substance of the latter. In the new-born child they may be already 

 present, but in many instances this is not the case. 



The mode of development of the lingual crypts is in its broad outlines 

 the same. 



250. 



The muscles of the pharynx are made up of striped fibres ( 164). 

 The tough mucous membrane of the lower portion is covered with simple 

 papillae clothed with laminated flattened epithelium. The upper part 

 (furnix), on the other hand, is quite destitute of these, and is covered in 

 the infant with ciliated epithelium, while in the adult body the latter is 

 replaced by the flattened species. This portion of the pharynx, farther, 

 is that most abundantly supplied with glands. These are, in the first 

 place, of the racemose mucous species, and then lymphoid organs men- 

 tioned in the preceding section. The mucous membrane of the pharynx 

 is very vascular, besides being abundantly supplied with lymphatic 

 canals. Interlacements of delicate nerve-fibres have also been seen in it 

 (Billrolh, Kodliker). 



We now turn to the oesophagus, which, n its strong external longitu- 



