X PREFACE. 



from 1876 to 1880, when I again resumed it with the aid of 

 assistance from Dr. Cash and others in the manner I have 

 already mentioned. From this time onward the pressure of 

 other engagements has only permitted me to do most of my 

 laboratory work by means of assistants in the manner I have 

 mentioned at the beginning of the preface. 



I am aware that for the majority of readers this preface is 

 too long and too personal, but they can easily pass it over, and 

 some of those friends (whose desire to read some of my old papers 

 has led me to republish them) may be interested to knov/ why 

 my experimental work on the circulation has apparently been 

 so fitful and so intermittent. 



