THE CAUSATION OF DISEASE. I I I 



the potentialities of remote ancestral actualities, which display them- 

 selves under modifications of cell environment. 



& As regards tumours, the nature of this environment is known in 

 certain instances, as in the granulomata : parasites enter the tissue, 

 and so disturb the cell environment that they can no longer maintain 

 their high grade of specialization, and revert in consequence to an 

 ancestral type. The malignant tumours have, I believe, a like para- 

 sitic origin : but there is no need here to adduce arguments in favour 

 of this view. Now, sarcomatous tissue is distinctly of an ancestral 

 type : one cannot, however, speak so positively of the carcinomatous. 

 In epithelioma, however, we see changes allied to embryological 

 ones. The squamous epitheliomata originate by an involution of the 

 epithelium, such as occurs in the development of all open glands 

 (even the liver is thus developed) ; but in this instance the invested 

 cylinders have no lumen ; nevertheless, the manner of development 

 is that of a crude form of gland. In the cylindrical variety we have 

 a higher effort, for a distinct lumen is developed. I cannot compare 

 the carcinomata with any embryological or ancestral tissue, through 

 dearth of knowledge ; but let us bear in mind that the affected tissues 

 must possess the potentiality of this mode of growth ; and whence, it 

 may be asked, have they this power 1 I should not be surprised if 

 one of wide histological knowledge could throw light upon the 

 subject by studying it on the lines laid down by Dr. Gresswell." 



It is certain that such reversions of a mature tissue to an 

 ancestral state play a very important part in pathology ; but 

 the subject stands in need of careful investigation. In this 

 connection gout at once occurs to mind. Abnormal quantities of 

 uric acid are produced in this disorder. Now, in certain classes 

 of animals the nitrogen is eliminated chiefly in the form of 

 uric acid, and the question arises whether gout be not such 

 a reversion. It is impossible to say, because we know practi- 

 cally nothing concerning the mode of production of uric acid, 

 and it may turn out that the physiology of uric acid in 

 mammals is fundamentally distinct from that in birds and 

 reptiles. However, this case of gout suggests to us that in 

 many diseases the process of reversion plays an important part. 

 If we bear in mind the countless potentialities of every 

 complex organism — potentialities derived from an untold 

 number of ancestors — we shall be the less inclined to think 

 the suggestion fanciful and unworthy of further investigation. 



