88 CM. JACKSON 



tion series (table 3). No published observations upon the nor- 

 mal cartilaginous skeleton are available for comparison. Pro- 

 fessor Donaldson of The Wistar Institute, however, has very 

 kindly sent me a series of observations upon the weight of the 

 cartilaginous skeleton in normal albino rats. The average, in 10 

 cases with body weight varying from 194 to 426 grams, forms 

 about 6.7 per cent of the (gross) body weight. In this series, 

 however, I understand that the intervertebral cartilages were 

 not preserved, so this figure is probablj^ somewhat too low for 

 use as a normal to be directly compared with my observations 

 upon the cartilaginous skeleton in inanition. The normal adult 

 cartilaginous skeleton, including the intervertebral cartilages, 

 would probably form about 7 per cent (or shghtly more) of the net 

 body weight. 



The dried cartilaginous skeleton (table 3) formed an average 

 of 5.48 per cent of the net body weight in 7 cases of acute inani- 

 tion, and 6.03 per cent in the 6 chronic cases. Thus it is evident 

 that in each series the cartilaginous skeleton is composed of ap- 

 proximately half dry substances and half water. In the acute 

 inanition series, the dry substance in the cartilaginous skeleton 

 averages 50.5 per cent (range, 45.1 to 54.6 per cent). In the 

 chronic series, the dry substance averages 49.2 per cent (range, 

 45.5 to 55.7 per cent). If case M 5 be excluded (which appears 

 to be exceptional or erroneous), the average for the chronic 

 series would be still lower, or 47.9 per cent. In any event, the 

 dry content appears to be slightly lower and the water content 

 correspondingly higher on the average in the chronic inanition 

 series, which might be expected. 



Data upon the normal composition of the skeleton of the rat 

 for comparison are scarce. In one case which I have observed 

 (at 10 weeks) the net body weight was 115 grams, ligamentous 

 skeleton 9.91 per cent of body weight, fresh cartilaginous skele- 

 ton 5.57 per cent, and dry cartilaginous skeleton 2.97 per cent. 

 In this case the dry substance formed 53.4 per cent of the car- 

 tilaginous skeleton. Lowrey ('13) in two albino rats (body 

 weight 267.5 grams) finds the ligamentous skeleton forming about 

 9 per cent of the body weight, and containing 52.6 (52.1 to 53.1) 



