RELATIVE WEIGHT AND VOLUME OF COMPONENT PARTS OF FETAL BRAIN. 45 



the various parts of the same brain. These results are probably due to the use of 

 crude apparatus and to a tendency to give results in round numbers. 



Ziehen (1903) includes 9 embryos in a large series of cases reported. The age 

 of 6 of these was 30 days and the recorded total brain-weights were respectively 0.98, 

 1.0, 1.05, 1.13, 1.15, and 1.15 grams; 3 were 29 days old and the total brain-weights 

 were 1.29, 1.23, and 1.15 grams respectively. All of the material has been preserved 

 in formalin. 



Michaelis (1907), in a number of cases of children autopsied by him in Leipzig, 

 reports 7 groups of embryos . Jackson ( 1 909) , in a study of prenatal growth, records 

 observations made upon 43 specimens ranging from 6 mm. to full term. In these 

 studies the measurements were by volume and not by weight, as in the other cases 

 recorded. The volume was determined in some cases by the amount of water dis- 

 placement of the brain of the embryo modeled in wax by the Born method; in others 

 by making enlarged drawings of the parts, measuring these drawings with a plani- 

 meter and calculating the volume by multiplying the areas by the thickness of the 

 sections. His conclusions are that the brain, although subject to considerable 

 variation, shows a fairly regular curve of growth. At the second month it forms 

 slightly more than 20 per cent of the total body-volume, the average dropping to 

 12.8 per cent in still-born fetuses. In the living-born, however, the average was 

 about 14.6 per cent. 



Dockeray (1915), working toward the same end which is the purpose of my 

 own paper, and using similar methods, gives a complete volumetric study of the 

 brain parts in a fetus 156 mm. in length, and I have incorporated his results in this 

 paper. 



METHODS AND MATERIAL. 



Two points in the technic employed in my own studies were determined upon 

 because their worth had been proved, both in this laboratory and by other workers: 



First, the use of the crown-rump or sitting-height as a standard for determining 

 the size of the material used: Both Le Bon (1879) and Donaldson (1909) agree 

 that body-length is a better criterion than body-weight from which to infer brain- 

 weight. The use of this method relieves us of the necessity of determining the leg- 

 length, an unsatisfactory procedure even in older fetuses. 



Second, the method of preservation: All of the material used in this study had 

 been preserved in formalin which alone in varying strengths, or in combination with 

 other agents, is by far the most universally used preservative for animal tissues. 

 Hrdlicka (1906) experimented with the effects of various preservatives upon the 

 brains of both human and lower vertebrates and found formalin the most satis- 

 factory. Though confirming in part the work of others who claim that this agent 

 causes an increase in volume in the tissues preserved in it, in his summary he states 

 that the simple formalin solutions all show the same effects in all brains. These 

 consist of a sharp initial rise in the weight of the specimen, reaching a maximum 

 within less than a week, and a subsequent gradual, long-continued decrease. The 

 rise is in inverse ratio to the strength of the formalin solution, the percentage of 

 loss being apparently independent of the formalin percentage. 



