30 MOTION OF THE 



heart will be found at the bottom of that orifice in the right 

 side of the body which is seen to be opened and shut in the 

 course of respiration, and whence saliva is discharged, the in- 

 cision being made in the upper aspect of the body, near the 

 part which corresponds to the liver. 



This, however, is to be observed: that in winter and the 

 colder season, exsanguine animals, such as the snail, show no 

 pulsations; they seem rather to live after the manner of vege- 

 tables, or of those other productions which are therefore de- 

 signated plant-animals. 



It is also to be noted that all animals which have a heart, 

 have also auricles, or something analogous to auricles; and 

 further, that wherever the heart has a double ventricle there 

 are always two auricles present, but not otherwise. If you 

 turn to the production of the chick in ovo, however, you will 

 find at first no more than a vesicle or auricle, or pulsating drop 

 of blood ; it is only by and by, when the development has made 

 some progress, that the heart is fashioned : even so in certain 

 animals not Destined to attain to the highest perfection in their 

 organization, such as bees, wasps, snails, shrimps, crayfish, &c., 

 we only find a certain pulsating vesicle, like a sort of red or white 

 palpitating point, as the beginning or principle of their life. 1 



We have a small shrimp in these countries, which is taken 

 in the Thames and in the sea, the whole of whose body is 

 transparent ; this creature, placed in a little water, has fre- 

 quently afforded myself and particular friends an opportunity 

 of observing the motions of the heart with the greatest dis- 

 tinctness, the external parts of the body presenting no obstacle 

 to our view, but the heart being perceived as though it had 

 been seen through a window. 



I have also observed the first rudiments of the chick in the 

 course of the fourth or fifth day of the incubation, in the guise 

 of a little cloud, the shell having been removed and the egg 

 immersed in clear tepid water. In the midst of the cloudlet 

 in question there was a bloody point so small that it disappeared 

 during the contraction and escaped the sight, but in the re- 



1 [The Editor begs here to be allowed to remark on Harvey's obvious perception 

 of the correspondence between that permanent condition of an organ in the lower, 

 and its transitory condition in the higher animals. ED.] 



