OF VITAL MOTION. 109 



the rhythmical movements of the heart are suspended 

 in winter, or else repeated so slowly as to escape the 

 attention of an ordinary observer, and the organ itself 

 so shrunk and contracted as to be little more than 

 an ordinary vessel, a change which, when compared 

 with the state in summer,- would seem to argue that 

 the heart has suffered contraction in consequence of 

 the coldness and inclemency of the season. 



The influence of extra-organic agents may also be 

 seen in the heart of a chick, if a visit be paid to the 

 hydro-incubating establishment of M. Cantello. The 

 other day, for example, I had ocular demonstration 

 of this, along with my friend Dr. William Addison. 

 On opening an egg of the third day the heart was 

 seen to pulsate regularly, and to continue to do so for 

 some after the embryo was separated from the vas- 

 cular area, and placed upon a slip of glass. When 

 the heart became still, which it did in a few minutes, 

 we found it possible to renew the action by placing 

 the lower surface of the glass in light contact with 

 the warm water which is used to hatch the eggs; 

 and when it was still a second time the rhythm was 

 renewable in the same manner. Indeed it was found 

 possible by this application of warmth to revivify the 

 heart when it ceased to act, until the organ and the 

 rest of the gelatinous embryo were half dried up by 

 exposure to the atmosphere. It was the same also 

 with an embryo-chick of the sixth day, which was 



