, The Journal of 



Comparative Neurology and Psychology 



Volume XVIII OCTOBER, 1908 Number 4 



A COMPARISON OF THE ALBINO RAT WITH MAN 

 IN RESPECT TO THE GROWTH OF THE BRAIN 

 AND OF THE SPINAL CORD. 



BY 



HENRY H. DONALDSON, 



Professor of Neurology at the JVistar Institute. 



With Plates II and III and One Chart in the Text. 



In this paper it is proposed to present data illustrating the 

 growth of the brain and spinal cord of the albino rat, and also to 

 compare their growth in this animal with that in man. 



As a preliminary to this study, it was necessary to determine 

 for the rat the growth curve of the entire body. The observations 

 on this point were published in 1906 under the title " A compari- 

 son of the white rat with man in respect to the growth of the entire 

 body" (Donaldson '06). In that paper it was shown that the 

 growth curve of the rat exhibited all the phases found in the human 

 growth curve, and, further, that the curves for the two sexes were 

 similarly related in both the forms examined. In the present 

 study, therefore, we shall have the advantage of examining the 

 growth of the nervous system in an animal, the general growth 

 curve of which is similar to that of man, and this fact should 

 enhance the significance of the results. 



The observations to be presented are unique, as the literature 

 contains no extended record of the growth of the brain and of the 

 spinal cord in any mammal below man. Moreover, the observa- 

 tions on man are open to a good many qualifying criticisms, and 

 it will be most advantageous, therefore, to postpone comment on 

 them until the data from the rat have been presented. 



This study of the rat was begun thirteen years ago, and during 

 the interval the records have been accumulating. Throughout 

 this period the rat colony has been composed always of the albino 

 variety of Mus norvegicus (Hatai '07), although occasionally, 



