1 1 6 ELE VEN TH LECTURE. 



ies made in the tonsils and trachoma follicles confirm what 

 follows. 



The chyle vessels of the intestinal villi (a), are the vasa 

 afferentia (p. 108). Passing further down, they form the 

 lymphatic net-work {g, i), which surrounds the follicle, as the 

 thread does the toy ball of the child. From these arise, at 

 the base of the follicle, the efferent lymphatics (/<;), compar- 

 able to the vas efferens of the lymphatic gland. 



The capillary net-work of the Peyer's plates appears extra- 

 ordinarily developed. Fine capillaries permeate the follicle 

 in a radial direction (Fig. no, a) ; additional tubes (b) form 

 a no less elegant interfollicular net-work. 



The thymus consists of lobular groups of a reticular con- 

 nective tissue containing lymphoid cells. The interior of the 

 lobule is hollow, connected on all sides with a convoluted 

 main canal. Here we also meet with an elegant capillary retic- 

 ulum, which differs in man and the calf in the arterial and 

 venous arrangement. The lymphatic passages require more 

 accurate investigation. The retrogression of the enigmatical 

 organ begins before and with puberty. Fat cells in great 

 quantity are developed at the expense of the lymphoid tissue. 



The spleen constitutes the most difficult organ of the lym- 

 phoid group. It has been the object of many researches in old 

 and modern times. We have, indeed, progressed further than 

 our predecessors, but much still remains a matter of contro- 

 versy. I here give only what I, after numerous personal 

 studies, regard as correct. 



Similar to a lymphatic gland, our organ is surrounded by a 

 fibrous envelope containing sometimes more, sometimes less 

 smooth muscular tissue. This sends off again, in an inward 

 direction, an interrupted system of septa. The latter, also 

 called the trabecular system of the spleen, is extensively de- 

 veloped in large mammals, while in small creatures (marmot, 

 rabbit, Guinea-pig, rat and mouse) only scanty rudiments of 

 it are met with. We are, therefore, once more reminded of 

 the lymphatic glands (p. 108). 



It is best to commence the investigation with one of the latter 



