864 



average weight of 218.7 grams, of which 93.38 grams of muscle 

 weight, with seven females of the same age, with an average weight 

 of 154.8 grams and a muscle weight of 65.94 grams, we find a 

 relati\e weight of the muscles of 42.7 7o ^or the males and 42.6 7o 

 for the females. For four male albino rats (Mus norvegicus ErxL), 

 of 365 days, weighing on an average 260.2 grams, the mean relative 

 weight of the muscles was 46.5 "/,, and two female albino rats, 

 weighing on an average 183.5 grams, had a mean relative muscle 

 weight of 43.3 7o- Calculated with the absolute muscle weights 761.8 

 and 517.1 grams') given by Wei.ckkk there was equality of relative 

 uiuscle weight (viz. 52.7 and 52.5 7o) between the cock of 1445.7 

 grams and the hen of 985.1 grams of body weight. For the above 

 mentioned almost full-grown Leghorn cock I found 213.9 grams or 

 11.9 7o of the body weight for the joint weight of the three left- 

 hand and the three righthand pectoral muscles; for the fullgrown 

 hen 174.6 grams or 14.6 7o o^ ^''^ body weight! In about the same 

 geoineti'ical ratio the muscles of the shank of the hen exceeded those 

 of the cock. Evidently the cock was less muscular, because it was 

 not quite full-grown. When the body weight of the cock is calculated 

 with equal relative muscle weight as the hen, the exponent of rela- 

 tion becomes 0.2984. An adult male and an adult female lizard 

 (Lacerta agilis L.) according to Welcker ') have almost the same 

 relative muscle weight ; so have a male and a female Spotted Land- 

 salamander (Salamandra maculosa Laur.) according to his data. 



But such a proportionality of body weight and muscle weight, 

 between individuals of identical species and equal sex, as well as 

 between the two sexes, may certainly be assumed, if this proportion- 

 ality also exists between diffei-ent homoneuric specie.^-. 



Very valuable data about this matter are furnished by A. Magnan "). 

 From the values which he gives for the average relative weights of 

 the musculus coraco-brachialis (which muscle raises the wing) in 

 different orders of Birds, taken in general (p. 126), proportionality 

 with the body weight already appears. But it seems to me to be of 

 importance to examine this within every order and also for the 



1) Welckek— Brandt, loc. cit., p. 53. — Falck's muscle weight corrected by 

 Welcker. Among these muscle weights for the cock and the lien also a crtain 

 part of the skeleton is included. 



2) Loc. cit., p. 55. 



3) A. Magnan, Relation chez les Giseaux entre le poids de leurs muscles 

 pectoraux et leur maniere de voter. Bulletin du Muséum national d'Histoire naturelle. 

 Année 1913, N'. 1, Paris 1913, p. 40—52. Les muscles releveurs de I'aile chez 

 les Giseaux. Ibid., m 2, p. 126—128. 



