THE CAUSATION OF DISEASE. 109 



3. In the different kinds of reversion hitherto considered, 

 the cause is an error or peculiarity in the process of develop- 

 ment ; but there is another kind of reversion, which is apt to 

 be left out of account — namely, the reversion of a mature 

 and properly developed tissue to a remotely ancestral state. I 

 Jhave already instanced the loss of the moral nature in the 

 commencement of an attack of insanity. In such a case, 

 the cortical tissue reverts to a state belonging to pre-moral 

 times. Now, all the tissues of the body exhibit a like ten- 

 dency to reversion. If the cell-E necessary to the maintenance 

 of a high state of evolution, be vitiated, we find the tissue 

 reverting to a more elementary form — to one belonging to a 

 remote ancestor. What, for instance, is the effect of an irri- 

 tant when applied to living tissues ? That curious process which 

 still continues to bother the pathologist occurs — inflammation. 

 Now, if an inflammation is not so slight as to end in resolu- 

 tion, nor sufficiently violent to destroy the tissue, the mature 

 tissue is replaced — as Cornil and Ranvier put it — by an 

 embryonic tissue ; in other words, there is reversion of the part 

 to a remotely ancestral state. Take, for instance, inflammation 

 of muscle-tissue : the mature muscle fibres disappear, and their 

 place is occupied by small round cells, amongst which small 

 capillaries presently develop, forming the so-called granula- 

 tion-tissue. If the irritant be removed, this tissue will attain 

 higher development : there will be an abortive attempt at the 

 production of muscle-tissue, although little more than fibrous 

 tissue will be formed. In round-cell sarcoma, the process 

 is similar. Sarcomatous and granulation-tissue are, I sup- 

 pose, fundamentally the same. In sarcoma, as I shall argue 

 in another part, the irritant, or as I should prefer to put it, 

 the mal-cell-E, consists of a specific bacillus. This consti- 

 tutes an abiding mal-E. Hence the morbid process is con- 

 tinuous, and the cells, being continually irritated, are prevented 

 from developing into a mature tissue. In the round-celled 

 sarcomata no higher development whatever is permitted, but 

 in the other varieties a faint effort is made in that direction. 

 In the epitheliomata, we probably have a similar reversion to 

 an elementary form of gland-tissue, and it may be that the 

 same is true of the acinous carcinomata. In the myxomata, 



