CAUSATION. — ANATOMICAL CHARACTERS. 279 



condition, instead of showing exhaustion, indicates plethora. 

 When observed in these latter conditions, however, it will be 

 found on examination that the animals, although to appear- 

 ance plethoric, are not in full and vigorous health; that the 

 fulness of body is the result of defective, unnatural and un- 

 healthy dietetic conditions, that the material upon which they 

 have been fed has not been calculated to produce healthy and 

 well-elaborated blood-tissue. 



Animals in either of these conditions Avhen exposed to such 

 direct adverse influences as proceed from improper location, 

 and particularly such as result from imperfect ventilation, 

 defective drainage, effluvia arising from decomposing animal 

 or vegetable matter, are extremely liable to experience a rapid 

 and full development of those tissue-changes which have 

 already been faintly traced out and rendered possible. 



Thus, although undoubtedly true that the causes acting 

 in determining the production of purpura may often seem 

 rather obscure or apparently conflicting, not operating with 

 what we may regard as uniformity, we may, nevertheless, see 

 through all cases traces of certain general laws which regulate 

 its appearance, and thus be able to follow in detail the inducing 

 agencies of many individual developments of the phenomena 

 characteristic of the disease. 



c. Anatomical Characfers. — The earliest and most exten- 

 sively affected tissue, the blood, is altered in general appearance 

 and intimate characters ; it is darker than natural, possessing 

 greater tenuity, or a disposition for the watery portion to 

 separate itself from the other constituents ; it is not disposed to 

 coagulate either in or without the vessels. Examined more 

 minutely, there is often a preponderance of watery constituents 

 and an alteration of the red globules ; these have in part 

 become destroyed; they are shrivelled in appearance, as if their 

 contained material had become lessened, and they occasionally 

 become heaped together in mass ; the amount of colourless 

 corpuscles is increased. 



The cutaneous swellings, which were so diagnostic during 

 life, show on removal of the skin a condition of infiltration 

 with more or less blood-stained imperfectly coagulated gelatin- 

 ous material, the infiltration extending throughout the subcu- 

 taneous connective-tissue, and the colouring matter, apart from 



