472 ANATOMICAL AND PATHOLOGICAL OBSERVATIONS. 



but if otherwise, a cicatrix only is formed, which remains 

 until the casting of the shell, when the new shell takes on 

 all the characters and appearance of the old one, before it met 

 with the injury. When the animal is weak and unhealthy, 

 and in that state meets with any severe injury of a limb, it 

 is unable to throw it off at the usual place, and consequently 

 very soon dies from loss of blood ; but when strong and 

 vigorous, it is enabled to throw the injured limb off with 

 little apparent pain or exertion. It is a well-known fact, 

 that these animals can throw off their limbs when seized by 

 them, and also from several other causes, to which it is 

 unnecessary to allude at present. 



When the crustacean does throw off a limb voluntarily, it 

 will be found on examination that this is always effected at 

 one spot only, near to the basal extremity of the first phalanx. 

 This part of the phalanx is very much contracted for the 

 length of half-an-inch, or a little more, in the common edible 

 crab. The whole of this portion is filled with a fibrous, 

 gelatinous, glandular-looking mass ; the organ which supplies 

 the germs for future limbs. On looking closely into the 

 surface of this body, we find that it is divided into two 

 unequal parts, by means of a transverse line. The basal or 

 proximal part of this body is the smallest. On tracing this 

 line towards the shell we find that it runs into it, as it were, 

 and forms, instead of one line, two ; by which means a very 

 thin ring is formed, and this ring is also found to run com- 

 pletely round the limb, being marked externally by means of 

 a thin band of small scattered hairs. By dissection this line 

 can be traced into the substance of the organ of reproduction, 

 and is found in this way to be the exact spot where the limb 

 is generally thrown off. Through the long axis of this, and 

 near to one edge, a small foramen exists for the transmission 

 of the bloodvessels and nerve. The microscopic structure of 

 this gland or organ is extremely beautiful. When a thin 



