2 Dr. Mac Culloch on the Means 



form that for which the utmost effort of its muscular powers ap- 

 pears to be requisite. Being unwilling to propagate a method of 

 adding to the torments of animals for the mere gratification of that 

 cruel curiosity in which physiologists have too often, and with 

 justice, been accused of indulging ; I will not here communicate 

 the method by which the animals of this tribe may be induced to 

 perform this voluntary mutilation ; but it is rather too well known 

 to children who have been brought up on sea-shores. 



It is, nevertheless, doubtful whether the effort itself is attended 

 with pain, whatever the previous torment may be ; as it seems 

 of ten. to be done without any apparent motive. The whole tribe is 

 of an .extremely ferocious and irritable character ; and with many, 

 particularly of the younger .animals, the mere attempt to take 

 them, even without actual contact, causes them to drop the two 

 hands, or larger claws. Others do it if confined in a box or 

 a glass of water ; and almost all of the smaller kinds, or half 

 grown ones, part with any claw by which it is attempted to 

 retain them. 



To render the description of this process intelligible, it will be 

 necessary to understand the general structure of the limbs of this 

 tribe. The accompanying sketch, fig. 1, is from one of the small 

 claws of the spider crab, being the species just at this moment 

 under my eye. The structure of the several parts, as well as the 

 form of the limb, is of course somewhat peculiar to this species ; 

 but the difference is not material among the whole, and the same 

 explanation and drawing will, with slight modifications, apply to 

 all the instances in which it occurs. Even if I had not acci- 

 dentally had this species at hand, I should have preferred it ; as 

 the structure of the suture where the separation takes place, is 

 rather more distinct and remarkable than in the other species 

 which I have examined. 



The limb of a crab consists of six parts, each of which has an 

 appropriate motion in two directions, by means of a pair of muscles 

 adapted to the nature and extent of the space to be described. In 

 the extreme joint, the motion of direct flexion, towards the body, 

 is -considerable ; but the extension is limited by the structure of 



