Chap. IV. EFFECTS OF USE AND DISUSE. 125 



the bodies of four wild rabbits, and of four large but not fattened lop-eared 

 rabbits, I find that on an average the wild are to the lop-eared in weight as 

 1 to 217 ; in average length of body as 1 to 1*41 ; whilst in capacity of skull 

 (measured as hereafter to be described) they are only as 1 to 1*15. Hence 

 we see that the capacity of the skull, and consequently the size of the 

 brain, has increased but little, relatively to the increased size of the body; 

 and this fact explains the narrowness of the skull relatively to its length 

 in all domestic rabbits. 



In the upper half of the following table I have given the measurements 

 of the skulls of ten wild rabbits ; and in the lower half of eleven thoroughly 

 domesticated kinds. As these rabbits differ so greatly in size, it is neces- 

 sary to have some standard by which to compare the capacities of their 

 skulls. I have selected the length of skull as the best standard, for in 

 the larger rabbits it has not, as already stated, increased in length so much 

 as the body ; but as the skull, like every other part, varies in length, neither 

 it nor any other part affords a perfect standard. 



In the first column of figures the extreme length of the skull is given in 

 inches and decimals. I am aware that these measurements pretend to 

 greater accuracy than is possible ; but I have found it the least trouble to 

 record the exact length which the compass gave. The second and third 

 columns give the length and weight of body, whenever these measurements 

 have been made. The fourth column gives the capacity of the skull by the 

 weight of small shot with which the skulls had been filled; but it is not 

 pretended that these weights are accurate within a few grains. In the 

 fifth column the capacity is given which the skull ought to have had by 

 calculation, according to the length of skull, in comparison with that of 

 the wild rabbit No. 1 ; in the sixth column the difference between the 

 actual and calculated capacities, and in the seventh the percentage of 

 increase or decrease, are given. For instance, as the wild rabbit No. 5 

 has a shorter and lighter body than the wild rabbit No. 1, we might have 

 expected that its skull would have had less capacity; the actual capacity, 

 as expressed by the weight of shot, is 875 grains, which is 97 grains less 

 than that of the first rabbit. But comparing these two rabbits by the 

 length of their skulls, we see that in No. 1 the skull is 3T5 inches in length 

 and in No. 5 2'96 inches in length ; according to this ratio, the brain of 

 No. 5 ought to have had a capacity of 913 grains of shot, which is above 

 the actual capacity, but only by 38 grains. Or, to put the case in another 

 way (as in column vn), the brain of this small rabbit, No 5 for every 100 

 grains of weight is only 4 per cent, too light -that is, it ought, according 

 to the standard rabbit No. 1, to have been 4 per cent, heavier I have 

 taken the rabbit No. 1 as the standard of comparison because of the skulls 

 having a full average length, this has the least capacity; 'so that it is 

 the least favourable to the result which I wish to show, namely, that the 

 brain m all long-domesticated rabbits has decreased in size, either actually 

 or relatively to the length of the head and body, in comparison with the 

 brain of the wi d rabbit. Had I taken the Irish rabbit, No. 3, as the 

 standard, the following results would have been somewhat more striking 



Turning to the Table : the first four wild rabbits have skulls of the 

 same length, and these. differ but little in capacity. The Sandon rabbit 



