as observed in the Tongue of the living Frog, Toad, fyc. 283 



globules that have escaped. This fact is interesting, as the 

 appearance of the rupture shows how much the tissue of the 

 capillary is capable of being distended : either the blood does 

 not always escape through the vessel, or the opening becomes 

 soon closed up; for I have frequently seen small tumours, 

 similar to that in fig. 6, and often larger, into which the blood 

 penetrated and was seen to circulate*. 



Muscles. — Muscular tissue is known to consist of minute 

 fibres, which present under the microscope the appearance of 

 straight tubes or cylinders, generally of the same thickness 

 throughout, but varying in different fibres. In general these 

 cylindrical fibres are closely packed together in a parallel di- 

 rection, and adhere together by means of a semifluid glutinous 

 substance possessing the properties of cellular tissue. Ac- 

 cording to Krause, these fibres, which are also frequently 

 known under the name of primitive fasciculi, vary in diameter 

 from 2T<jth to J^th of a line. In the human pharynx, accord- 

 ing to Schwann, they are from T J 7 tn to To tn °^ a ^ ne# 



In certain parts of the body we find that these fibres pre- 

 sent under the microscope dark lines or streaks in the direc- 

 tion of the transverse diameter,resembling the steps of a ladder; 

 other fibres, on the contrary, are simple tubes without any 

 striae, and perfectly plain. The striated fibres were supposed 

 for some time to belong exclusively to the muscles endued 

 with voluntary action, and the latter to those removed from 

 the influence of the will. But although such is generally 

 the case, it has been found that this rule is not without excep* 

 tion. It has been remarked, that all the involuntary muscles 

 with striated fibres are very red and fleshy, and that the vo- 

 luntary muscles which are without them are pale and thin. 



The muscular striae have been the subject of great contro- 

 versy. By some they are considered to consist of globules, 

 which bv their close arrangement in a line create a striated 

 appearance. A hollow cylinder, such as the fibre appears to 

 be, is supposed to contain these globules within it : the inter- 

 mediate spaces are supposed to be light, from the absence of 

 the globules, and to be occupied by some transparent fluid. 

 This is the opinion advocated by Prevost, Dumas, Miiller, 

 Edwards, Home, &c. 



Having given these brief preliminary details, I will now 

 describe the muscular parts as they are seen in the tongue of 

 the frog and toad. 



Below the epithelium and papillae are seen the muscular 



* At some points there' exist in the minuter veins considerable constric- 

 tions. These are the valvules of the veins, and are not to be confounded 

 with any abnormal condition. 



U2 



