NATURAL HISTORY. 55 



The strength of animals of the same species is I believe best known 

 in their fighting ; yet, as that depends so much on the strength of mind, 

 and the two not always going together, this does not become an absolute 

 ride : but all this respects voluntary strength only. However, I believe 

 that in some degree, constitutional strength keeps pace with voluntary 

 strength. Thus, the males of any species can commonly beat the 

 females of the same species, which is voluntary : and we find that the 

 constitutional strength of the male is stronger than the female. Then 

 the male grows faster and larger; he is earlier for the female than 

 she is for him : but, the difference in strength of constitution is, per- 

 haps, best measured in the growth of transplanted parts ; viz. between 

 the spurs of a cock and those of a hen. 



"We know that the spur, or what may be called the rudiment of a spur, 

 in a hen, remains the same through life, only growing in proportion to 

 the size of the animal, like any other part : but, the spur of a cock 

 does more ; it shoots out at a certain period of life and grows much 

 faster than any other part. 



To know what this difference was owing to, whether it was not the 

 nature of a hen's spur to grow at all, or whether the hen had not that 

 vigour of constitution requisite to make it grow, I made the following 

 experiments. I removed the spur of a young cock and the spur of a 

 young pullet, and changed the spurs by what is called transplanting 

 them. Each spur united to the parts on which it was placed. Time 

 now could only determine the event. In a few months I found that 

 the spur taken from the pullet [and transplanted on the young cock] 

 began to grow, although not nearly so fast as the spur on the other 

 leg ; and in time it became a tolerably sized spur. The cock's spur 

 on the hen's leg did not grow for years, which made me at first sup- 

 pose that the spur of a cock would not grow on any animal but a cock : 

 nor did they ever grow to that size on the hen that the fellow spur 

 which was allowed to remain on the cock did. 



From the above experiment, it would appear that the spurs of hens 

 do not grow because there is not that vigour of circulation, or living- 

 powers, in the hen which exists in the cock ; but still there is a weak- 

 ness of growth in the hen's spur itself; for it does not grow upon the 

 cock equal to his own spur. As the weakness of growth of the cock's 

 spur upon the hen may not be attributed to a weakness of power in 

 the hen, nor the weakness of growth of the hen's spur upon the cock 

 be attributed to a weakness in the hen's spur, but to the circumstance of 

 transplanting, independently of everything else, I made the following- 

 experiments. 



As the comb of a cock appears to have' more blood, and of course 



