109 



fig. 3, the lines indicating the cut edges of the horny laminae are 

 seen terminating at the arches of cuticular cells, upon which they ap- 

 pear to rest, without being continued into them, whilst in the trans- 

 verse section through the nail at the lunula, represented in PI. 22, 

 fig. 4, the lines showing the cut edges of the horny lamina? are seen 

 to be continued into the small projections which are situated directly 

 upon and between the convolutions of the horn vessels. Besides the 

 microscopic examination of these substances, a difference in the pro- 

 perties of that covering the vessels of the lunula, and the other lying 

 upon the vessels of the other parts of the matrix, is shown by the fa- 

 cility with which these admit of being separated one from the other 

 on removing the nail from its matrix. Sometimes, after such a sepa- 

 ration, a layer of material remains upon the vessels of the lunula exactly 

 corresponding to them both in form and extent, those of the other 

 parts of the matrix being perfectly freed from all secretion, whilst 

 at other times the material remains, after the detachment of the nail, 

 upon the latter vessels, those of the lunula being completely denuded. 

 From all the facts which have been stated, I feel satisfied in my own 

 mind that the vessels of the lunula are exclusively those which are 

 employed in the secretion of the horny part of the nail, and that the 

 vessels in the longitudinal folds of the matrix which are continued in- 

 to the ridges of the skin, secrete merely cuticle. I have no opinion 

 to offer respecting the function of the lacuna? and the straighter ves- 

 sels, namely, those situated between the vessels of the lunula and 

 those contained in the longitudinal plicae, excepting that vessels in- 

 termediate in their position, as well as in their anatomical character, 

 between those secreting the horn and those the cuticle, may possibly 

 serve to furnish a substance intermediate in its properties between the 

 horny and cuticular part of the nail, and in this way cause a more 

 intimate union between these two substances at the instant of their 

 secretion, and preserve more completely the connexion of the nails 

 with the cuticle during the progress of their growth and protrusion. 



TRANS. MIC. SOC. VOL. II. 



