484 University of California Publications in Zoology [Vol. 13 



influences their volume. This error was reduced to a minimum, 

 however, by keeping the specimens well moistened with water 

 during dissection, and by being careful that before immersing the 

 structures they were neither too dry nor contained an excess of 

 water. The fact that the preservative used (80 per cent alcohol) 

 abstracts water from tissues and reduces their volume is of no 

 importance since only relative volumes are required, and all meas- 

 urements were taken in exactly the same manner. If weight had 

 been used as a criterion of strength, the amount of water in the 

 tissues would have caused as great an error as in the volumetric 

 method. 



The mammals used were usually skinned in the fresh state, but 

 sometimes they were placed in the preservative before being skinned, 

 the abdomen and thoracic cavity being always well injected with 

 alcohol. In either case, when the animal was skinned care was 

 taken to dissect out and save as much of the cutaneus maximus 

 muscle as possible. After the specimen had been left in the pre-^ 

 servative for several days to harden, dissection was begun by care- 

 fully separating and detaching at their origins and insertions the 

 muscles which bind the anterior limb to the body. As each muscle 

 was removed its volume was measured, as described above. When 

 all the muscles which hold the leg to the body had been removed, 

 the sternoclavicular articulation was separated, and the volume of 

 the detached leg was measured. To this figure the sum of the 

 volumes of the shoulder muscles already removed was added, and 

 the total volume was considered as 100 per cent. The muscles of 

 the leg proper were then dissected out and measured separately in 

 the same way. After all the muscles had been removed the volume 

 of the leg skeleton, including the scapula and clavicle, and the 

 hand, was measured. The volumes of the muscles composing each 

 different group were now added, and the bulk of the whole func- 

 tional group obtained. Finally, the percentages of the volumes of 

 each group to the total volume of the leg was determined. The 

 results, of these computations are given in table 1, p. 485. No actual 

 volumes are given in the table, all volumes being reduced to per- 

 centages of the total bulk of the leg and shoulder, in order to make 

 them comparable. 



It will be noted that the total volume accounted for is less than 

 100 per cent. This is due to the fact that in dissection it was 

 necessary to remove various structures, such as fat, fascia, blood 



