276 MOVEMENT 



it inight be used in all cases in which neither ordinary 

 observation nor the employment of the graphic method 

 could give us any definite information. 



There are also many curious movements in the 

 vegetable kingdom which can be studied by means of 

 chronophotography, such, for instance, as the sudden 

 retraction of the leaves and petals of the sensitive plant 

 when touched, the gradual return of these structures 

 to their original position, the progress of vegetable 

 growth, the unfolding of leaves, and the blossoming of 

 flowers. 



Successive photographs, taken at more or less fre- 

 quent intervals of time, will show the various phases of 

 these phenomena. 



In both kingdoms the microscope reveals deep down 

 in the midst of living tissues movements of immense 

 interest, for they are concerned with the fundamental 

 principles of organic life. Of such a nature is the 

 circulation of blood corpuscles in the finest capillaries, 

 and such is the movement of the zoospores in the cells 

 of algae ; such is the slow alteration in shape of the 

 white corpuscles of the blood, and the phenomenon of 

 phagocytosis, etc. It would be a very interesting study 

 to ascertain the characters of these movements by 

 means of photography. 



To give an instance of the advantages of chrono- 

 photography as applied to an experimental problem in 

 physiology, we will take the case of cardiac movements. 

 This is a subject which has been exhaustively studied 

 by means of the graphic method; nevertheless, chrono- 

 photography has afforded much new information of 

 quite a different kind ; we will summarize the question 

 as it stands at present. 



Analysis of Cardiac Movements by means of the 

 Graphic Method. — About thirty years ago, we, together 

 with our friend and colleague Chauveau, suggested at 



