THE GROWTH OF THE BRAIN AND VISCERA IN THE 

 SMOOTH DOGFISH (MUSTELUS CANIS, MITCHILL) 



BY 



WILLIAM E. KELLICOTT 



From the Biological Laboratory, The Woman's College of Baltimore, Md. 



Current ideas regarding the growth of animals are based to a consider- 

 able extent upon observations on the weight or length of the entire 

 organism. And yet it is well known that the proportions of many 

 external parts regularly change during growth and that at least one 

 internal organ, the brain, does not increase in weight at the same rate as 

 the whole animal. The question comes quite naturally then whether 

 other parts than the brain may not also have their own rates or cycles of 

 growth which may differ more or less from the type of growth given by 

 the entire organism. Physiologists are showing- that in many instances 

 certain organs or tissues may show regular, sometimes recurrent, growth 

 cycles quite independent of the growth of the body as a whole and we 

 are led to inquire whether the normal growth of an animal may not be 

 actually a complex of growth cycles of component parts. It is quite 

 possible to examine this question from the morphological as well as from 

 the physiological side, and the present paper represents an attempt to 

 discover whether the brain and viscera of the dogfish grow similarly or 

 in diverse ways, as somewhat independent units of growth. 



We are remarkably deficient in our knowledge regarding the normal 

 growth of the viscera or of parts of the body other than the brain. 

 Doubtless much valuable information of this kind regarding man lies 

 concealed in hospital and clinical records. But, as far as I have been 

 able to discover, the meagre data collected by Welcker and Brandt, '02, 

 and by Vierordt, '06, represent the extent of our knowledge regarding the 

 growth of the viscera in man and other vertebrates. 



It seems that this lack of information concerning the growth of parts 

 has led to a partial misconception of what is involved in the growth of 



The American Journal of Anatomy. — Vol. VIII, No. 4. 



