EDITOR'S PREFACE. vii 



ties of witnessing his experiments. The views of Hermann and Rad- 

 cliffe on Electrotonus, and of Kiiss on Reflex Actions, are fully given, 

 and an attempt has been made to supply an outline of Meynert's obser- 

 vations on the Structure of the Brain. 



In the account of the Circulating System considerable pains have 

 been taken to give a connected account of the numerous experiments 

 that have been made within the last few years on the Action of the Ner- 

 vous System upon the Heart, and the Editor must acknowledge the 

 kindness of Dr. Bruuton in revising the proof sheets of this part. 



Free use has been made of the Elements of Embryology by Dr. 

 Foster and Mr. Balfour, in describing the earlier stages of development, 

 and several of the drawings have been borrowed from this excellent and 

 instructive work. 



The Editor regrets that the Memoir of Dr. Buchanan on the Forces 

 which carry on the Circulation of the Blood was overlooked when this 

 subject was under consideration, or he would have been disposed to 

 accord a somewhat greater influence to the respiratory actions in pro- 

 moting the flow of Blood through the Heart than is admitted in the 

 text. And, again, in regard to the circumstances affecting the fre- 

 quency of the Pulse, reference should have been made to Mr. Garrod's 

 observations. Mr. Garrod maintains that the Pulse rate varies inversely 

 as the arterial capillary resistance, and is not affected by the arterial 

 blood-pressure, grounding this essentially on the fact that no effect is 

 produced on the blood-rate in an animal bled to death under chloroform, 

 from which he deduces the law that the heart recommences to beat after 

 the diastole, when the blood-pressure has fallen a certain invariable pro- 

 portion a law, the possible hyclrodynamical complications of which are 

 much simplified by the verified observations of Poisseuille, who demon- 

 strated that the flow of fluids through capillary tubes varies directly as 

 the pressure. 



A considerable number of woodcuts, most of them of a diagrammatic 

 character, have been added, and a few of the older ones have been 

 replaced by others giving better representations of the objects described 

 in the text. 



HENRY POWER. 



GREAT CUMBERLAND PLACE, 

 Nov. 1875. 



