76 ANIMAL PHYSIOLOGY. LESSON 25. 



416. The vascularity of the bed, or matrix of the nail, is an ob- 

 ject of great interest; these vessels differ entirely in their form, ar- 

 rangement and size, from the capillaries of the cutis vera (true skin), 

 as may be seen by reference to Fig. 113. The capillaries of this tis- 

 sue are remarkable for their extreme fineness and parallelism ; their 

 function appears to be to secrete the horny layer, which forms the 

 true substance of the nail. The vessels of the cutis vera (true skin) 

 everywhere surround the vessels of the matrix, the terminal looped 

 capillaries of the papillae of the skin being distinctly visible. 



417. In that horribly severe and excruciating operation of what 



is called minor surgery (!), the removal of 

 a nail because its edges grow inwards, and 

 produce great pain, associated with con- 

 stant irritation, the unfortunate patient 

 frequently desires to know " if the nail 

 will grow again." The answer to this 

 anxious question is generally very vague, 

 " sometimes it does, and sometimes it does 

 not." A little practical physiology would 

 enable the operator to give a positive an- 

 swer " It shall either grow again, or not, 

 at your pleasure." If the peculiar stra. 

 raiL turn of vessels just examined be included 

 in the operation, the nail can never grow again, as the vessels which 

 produce it are gone, and there is no power in the human subject (or 

 higher mammals) to reproduce lost parts : they, therefore, once re- 

 moved, can never be replaced, and their function is gone. 



418. It appears to be bad surgery, however, to remove an entire 

 nail for the fault of its edges ; they alone should be removed, care 

 being taken to include these particular vessels, with the offending 

 portion of the nail. 



419. The horny hoofs of horses, sheep, oxen, pigs, &c., are all 

 formed by a similar layer of vessels, which, when minutely injected 

 and well displayed, form objects of exceeding beauty, particularly 

 the vascular lamellae of the Horse's hoof, which is intended to act as 

 a series of beautifully elastic springs. Notwithstanding the exquisite 

 sensibility of this especial vascular layer, the terminal loops of the 

 nerves have hitherto escaped detection. 



