i8 THE FROG chap. 



made in the skin of the belly, and a probe pushed in under it, 

 it will be seen that the skin, instead of being firmly attached 

 to the underlying flesh, as in a rabbit or a sheep, is for the 

 most part quite loose, a spacious cavity lying between it 

 and the flesh. Not, however, a single continuous cavity 

 for the whole body : the probe, gently pushed in various 

 directions, is stopped, in front, at about the level of the 

 arms ; behind, at the junction of the thighs with the trunk ; 

 and at each side, along an oblique line joining the 

 armpit with the thigh. Moreover, by opening the 

 skin of the back, throat, and limbs, and inserting the 

 prpbe as before, similar cavities will be found in these 

 regions, all separated from one another by partitions, 

 along which the skin is firmly united to the underlying 

 flesh. It will be noticed also that the probe, when with- 

 drawn from any of these cavities, is wet. The cavities 

 contain a watery fluid, called lymph, and are hence known 

 as subcutaneous lymph sinuses (Fig. 7, d. ly. s, v. ly. s). 



When the skin is removed it will be seen that under 

 the skin and separated from it by the lymph-sinuses is a 

 nearly colourles.s, semi-transparent, fibrous substance, the 

 flesh. At first this appears to be continuous over the whole 

 body, but, by careful dissection with a sharp scalpel, a 

 very delicate, transparent skin, called the fascia, can be 

 separated from the flesh, which is then seen to consist of 

 a number of separate bands (Fig. 2, pet, my. hy, etc. ; see 

 also Fig. 16), covered as aforesaid by the fascia, and 

 separated from one another by a kind of packing substance, 

 also very delicate and transparent, and known as 

 connective-tissue. These bands or sheets are the muscles, 

 and the whole of the flesh is made up of distinct muscles, 

 readily separated from one another when once the requisite 

 anatomical skill is attained. Here and there — for instance 



