Vermifonn A2rperidix. 345 



their containing tissues determine ; therefore lymphoid cells 

 cannot compel form. The atrophic caecum of the cat has no 

 vermiform appendix. It has as much, or about as much, 

 lymphoid tissue as the human vermiform appendix. (Fig. 6.) 

 The law governing lymphoid tissue must be the same in a cat's 

 caecum as in a man's caecum. As the lymphoid tissue is equal 

 in each case and the shape differs, the statement that lymphoid 

 tissue compels form is denied by the cat's caecum. During 

 recession of the caecum it is quite possible to believe that 

 lymphoid tissue may offer some obstacle to atrophic processes 

 by affording the muscular walls a content grip — a totally dif- 

 ferent process from the development of the appendix for 

 lymphoid protection. To accept the idea that the appendix 

 develops for the protection of lyiuphoid tissue in a caecum that 

 has reached an advanced stage of atrophy compels one to believe 

 that a duality of processes (atrophy and hypertrophy), each 

 opposing the other, occurs at the same time in the same caecum. 



The pig has a Peyer's patch about six feet long, and yet for 

 the reception of this vast expanse of lymphoid tissue no ap- 

 pendix ia developed. One wonders how this mass of lymphoid 

 tissue manages to exist without a vermiform appendix when we 

 are asked to believe that the insignificant amount of lymphoid 

 tissue in the human appendix is the cause of the development of 

 vermiform appendix. If lymphoid tissue compelled the vermi- 

 form appendix to develop, the intestinal tract should be studded 

 with vermiform appendices wherever lymphoid tissue occurs. 

 If lymphoid cells compel the shape of the human appendix, they 

 also compel the shape of the wombat's vermifonn appendix. 

 The vermiform appendix of the wombat contains no different 

 amount of lymphoid tissue from what is normal to the intestine. 

 We have sectioned the vermiform appendix of three different 

 wombats. In two of these the sections fail to show any lymphoid 

 tissue. Mr. W. Fielder kindly sectioned a wombat's appendix 

 for us ; his first sections were like ours, negative. On prolonged 

 search he discovered solitary follicles, a condition which he con- 

 siders normal to the caecum. (Fig. 18.) 



We have been unable to find any test which, applied to the 

 lymphoid tissue of the human appendix, would lead us to l)elieve 

 that lymphoid tissue is the cause of the development of the 



