40 MAX MAYO MILLER 



of its various regions and parts. To throw light upon this matter 

 the present study was undertaken. The data here presented 

 include: First, the absolute and relative growth of the spinal 

 cord in its entirety ; second, the absolute and relative amounts and 

 the rate of growth of the different regions of the cord ; and third, 

 the absolute and relative amounts and the rate of growth of the 

 gray matter, of the white matter and of the ependyma with the 

 canal. This investigation was carried on in the Anatomical 

 Laboratory of the University of Missouri, under the direction of 

 Prof. C. M. Jackson, to whom I am also indebted for the use of 

 his collection of human embryos. 



MATERIAL AND METHODS 



The material used consisted of the following embryos: 11 nun. 

 (No. 60, fifth week), 17 mm. (No. 58, sixth week), 31- mm. (No. 

 57, eighth week), 65 mm. (No. 55, twelfth week), and 150 mm. 

 (No. 54, five months). The lengths are all crown-rump meas- 

 urements. The ages are only approximate and all conclusions 

 referring to them are, therefore, subject to more or less 

 uncertainty. 



The embryos had been prepared by the following methods: 

 No. 60 ( 9 ?) was fixed and hardened in alcohol, stained in bulk 

 in alum-cochineal, embedded in paraffin, and cut into transverse 

 serial sections, 20 /i thick. No. 58 (9) was fixed in formalin, 

 hardened in alcohol, decalcified in acid-alcohol, stained in bulk 

 in alum-cochineal, embedded in paraffin, and cut into transverse 

 serial sections, 20 fx thick. No. 57 (9) was fixed in formalin 

 hardened in alcohol, decalcified in acid-alcohol, stained in bulk 

 in alum-cochineal, embedded in paraffin, and cut into transverse 

 serial sections, 20 m thick. No. 55 {&) was fixed in formalin, 

 hardened in alcohol, decalcified in 1 per cent HCl in 70 per cent 

 alcohol, stained in bulk in alum-cochineal, embedded in paraffin, 

 and cut into transverse serial sections, 50 n thick. No. 54 (9) 

 was fixed in formalin, decalcified in 2 per cent nitric acid in 70 

 per cent alcohol, embedded in celloidin, cut into transverse serial 

 sections, 100 ix thick, and stained with alum-haematoxylin. This 

 material is all in good condition, especially the younger embryos. 



