EXPERIMENTS OF HALES. 77 



The changes of the vital process, caused by the Fishes die 

 unequal distribution of fluid in the body in conse- cause 'the 



distribution 



quence of evaporation, are best seen in animals of the fluids 



which live in water, in whom, therefore, the above vented. 



explained cause of motion in the normal state does 



not act. When a fish is held immersed in water, 



so that the head is out of the water, while the rest 



of the body is covered, it dies in a few minutes. It 



dies exactly in the same way when head and gills 



are held in the water, and the body in air ( MILNE 



EDWARDS) ; in both cases, without loss of weight. 



This fact shews that even if the weight of the 



animal be kept unaltered by the absorption of 



water through the body kept in that medium, yet 



the distribution of the fluids in the body does not 



take place in the proportion necessary for the 



preservation of their vital functions. The fish 



dies. 



It is hardly necessary to remind the reader, that 



the experiments described in the foregoing pages, HALES* on 



in so far as they permit us to draw conclusions as O f 

 to the cause of the motion of the juices of the mplai 

 animal body, agree in all respects with the observa- 

 tions made on plants by STEPHEN HALES more than 

 120 years since. 



The experiments of HALES on the mechanism of 

 the motion of the sap, may stand as a pattern to all 

 times of an excellent method. That they remain, 

 to this moment, unsurpassed in the domain of 

 vegetable physiology, may be perhaps explained by 



