240 THE AMERICAN MONTHLY [July, 



On a New Method of Studying Cell Motion. 



By CHAS. LESTER LEONARD, M. D., 



I'llILADKLfHIA. PA. 

 [From Proceed iiijis of the .Veadcmy of Natural Siiiences.] 



Since the enunciatiou by Vircliow, in 1858, of his the- 

 ory of cellular pathology, the attention of the scientific 

 world has been centered about the study of this unit. 

 Nearly all tlie unsolved problems of medical science in- 

 volve, in one way or another, the consideration of some 

 one of the functions of the cell. 



It is my purpose in this paper to call attention to a new 

 method of studying one of these functions. I have chosen 

 as illustrations, some of the well-known facts of physiol- 

 ogy already seen and described by competent observers, 

 and have confined the greater part of my study to cell 

 motion as exemplified in the movements of the red and 

 white blood corpuscles. 



The possibility of these studies was suggested by the 

 successful result of an experiment in instantaneous pho- 

 tomicrography. 



The method to be illustrated consists in the making 

 of a consecutive series of instantaneous photomicrographs 

 of the same microscopic field taken at definite intervals, 

 and the comparative study of the series. The results 

 obtained by this method are the elimination to a greater 

 extent of the personal equation of the observer, the pro- 

 curing of incontestable proof of }>henomena observed, 

 the extension of the observations over any length of 

 time, and the possibility of studying the changes occur- 

 ring over the entire field at any one moment. The 

 method also enables the student to study the condition 

 of a fresh, living, unstained specimen for any length of 

 time, in fields taken at definite intervals. 



The original magnifications were one and two-thous- 



