PARTS OF ANIMALS, III. v. 



biggest channels persist whereas the smallest ones 

 quickly get obliterated by the mud, though when 

 the mud abates they reappear ; so in the body the 

 largest blood-vessels persist, while the smallest ones 

 become flesh in actuality, though potentially they 

 are blood-vessels as much as ever before. Accordingly 

 we find that, as long as the flesh is in a sound con- 

 dition, wherever it is cut, blood will flow ; and 

 although no blood-vessels are visible, they must be 

 there (because we cannot have blood without blood- 

 vessels) — just as the irrigating channels are there 

 right enough, but are not visible until they are 

 cleared of mud. 



The blood-vessels get progressively smaller as they 

 go on until their channel is too small for the blood 

 to pass through. But, although the blood cannot 

 get through them, the residue of the fluid moisture, 

 which we call sweat, can do so, and this happens when 

 the body is thoroughly heated and the blood-vessels 

 open wider at their mouths. In some cases, the sweat 

 consists of a blood-like residue ° : this is due to a bad 

 general condition, in which the body has become loose 

 and flabby, and the blood watery owing to insufficient 

 concoction, which in its turn is due to the weakness 

 and scantiness of the heat in the small blood-vessels. 

 (We have already said that all compounds of earth 

 and water are thickened by concoction, and this cate- 

 gory includes food and blood.) The heat may, as 

 I say, be in itself too scanty to be able to cause 

 concoction, or it may be that it is scanty in comparison 

 with the amount of food that enters the body, if 



See A. E. Garrod, Itiborn Errors of Metabolism, Oxford, 1923, 

 pp. 136 ff. Also H. Giinther, Deutsches Archiv /. klin. 

 Medizin, 1920, 134, PP- 257 fF. 



253 



