18 THE FROG CHAP. 



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 probe 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 probe, when withdrawn from any of these cavities, is 

 wet. The cavities contain a watery fluid, called lymph, 

 and are hence known as sub-cutaneous 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 colourless, 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 membrane, called the 

 fascia, can be separated from the flesh, which is then seen 

 to consist of a number of separate bands (Fig. 2, my. hy, 

 pet, ret. abd ; 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 on the top of the head 

 and the front of the shanks there are no muscles, 



