78 CM. JACKSON 



cent of the body weight daily. This is usually found insufficient 

 for the maintenance of body weight in adult albino rats at ordi- 

 nary room temperature. One rat (No. M 4) was found dead; 

 the others were killed. 



At the end of the experiment, in both acute and chronic in- 

 anition, the rats were killed by chloroform and the various 

 organs and parts carefully dissected and weighed. The techni- 

 que followed is that described by Jackson ('13) and Jackson and 

 Lowrey ('12). The skeleton was first prepared as heretofore by 

 carefully dissecting off the musculature, leaving the periosteum, 

 ligaments and cartilages intact. This is recorded as 'ligamentous 

 skeleton.' In most cases the periosteum and ligaments were then 

 removed by maceration for about one hour in 1 per cent 'gold 

 dust' solution, following which the bones were cleaned under water 

 with forceps and camel's hair brush.- So far as possible, the 

 cartilages, including the intervertebral disks, were left intact and 

 included with the skeleton. The skeleton was then taken from 

 the water (excess moisture removed by filter paper) and weighed 

 as 'cartilaginous skeleton.' The skeleton was then dried for 30 

 days in a dust-proof case at ordinary room temperature. This 

 was found insufficient to remove all moisture, so the skeletons 

 were finally dried several days in an oven at about 90°C., until a 

 constant weight was reached. 



Portions of the various tissues and organs were preserved for 

 histological study, which will be considered in a later paper. 



As heretofore, in calculating the percentage weights, the net 

 body weight (gross body weight less intestinal contents) is taken. 

 The percentage weights of the organs are therefore slightly 

 higher than they would be if calculated upon the basis of the 

 gross bod}^ weight, but the difference is usually negligible, as 

 the intestinal contents form only 2 or 3 per cent of the body 

 weight during inanition. 



^ For this method of preparing the cartilaginous skeleton, I am indebted to 

 Professor Donaldson of The Wistar Institute. He states (in a personal com- 

 munication) that the fresh skeleton is apparently slightly reduced (about 3 per 

 cent) in weight by the 'gold dust' treatment, but this difference is so small as to 

 be practically negligible. 



