344 Stapley and Lewis : 



microscopic anatomy. Tliat which the microscope makes clear 

 is not the form of the tissue-mass from which the section Avas 

 made, but the histological elements of which the mass is com- 

 posed. 



Years ago Owen saw that the peculiarity of the rabbit's 

 caecum Avas that lymphoid tissue formed the caecal end. He 

 microscoped it (Fig. 4) ; he also miscroscoped the human vermi- 

 form appendix (Fig. 5). He described the lymphoid tissue in the 

 rabbit's caecal end as miassed lyn^phoid tissue, while he de- 

 scribed the appendix of man as containing less lymphoid tissue. 

 It did not occur to Owen, on account of the presence of this 

 naassed lymphoid tissue, to name the end of rabbit's caecum 

 vermiform. Owen did not I'egard the rabbit as showing that 

 rare form of caecum which he thought of under the name of 

 yermiform appendix. 



Lockwood at a later date emphasised the presence of lymphoid 

 tissue in the human appendix. Mitchell, on account of the 

 lymphoid end of the rabbit's caecum, calls it " the vermiform 

 appendix of the rabbit." (Fig. 3.) To quote him, " The rab- 

 bit's, caecum is capacious and ends, as is well known, in a 

 finger-shaped, narrow, thick-walled vermiform appendix." Since 

 this loose description was adopted all sorts of caecal ends have 

 erroneously been dubbed vermiform. No valid reason has yet 

 appeared for repressing the original meaning of the word 

 vermiform and twisting it to mean digit if orm or distorting it to 

 mean lymphoid. 



The " abdominal tonsil " theory of the appendix has resulted 

 from confusing things that are distinct in structure and form. 

 Berry and Ellenberger have accepted the lymphoid! tissue of the 

 caecum as the agent that compels the vermiform appendix to 

 come into being. To quote Berry, '' The vermiform appendix is 

 a part of the alimentary canal specialised for lymphoid function, 

 and not a vestigial remnant.'' 



Lymphoid tissue in an atrophic vermiform appendix should 

 be regarded from many view points before it can be accepted 

 as the causation of the appendix. That this lymphoid tissue is 

 not drawn up and enmeshed in tissues during the recession of 

 the caecum is not yet proven. The basis of lymphoid tissue is 

 round cells. A mass of round cells must assume that shape which 



