SECTION OP SKIN. 



677 



puscles, when floating in their own serum, or after having 

 been treated with acetic acid or water, appear to be fur- 

 nished with perfectly plain coverings, composed of a simple 

 homogeneous membrane, without distinction of parts. But, 

 when the blood is treated with a solution of magenta (nitrate 

 of rosanilin) or with a dilute solution of tannin, the cor- 

 puscles present changes which seem irreconcileable with 

 such a proposition. Dr. W. Eoberts, of Manchester, com- 

 municated an account of his observations on this subject to 



Fig. 313. A vertical section of the Human Skin, showing the sweat-glands, sur- 

 rounded by fat-globules, the ducts passing upwards through the epithelial 

 layer to the epidermis or external cuticle, magnified 250 diameters. 



the Royal Society (Proc. Roy. Soc. vol. xii, p. 481), in 

 which he shows that nearly every disc possessed a parietal 

 macula, capable of being stained by a dye. It was com- 

 monly of a lenticular shape, but sometimes square, and as 

 a rule very minute, not covering more than I -20th or l-30th 

 of the circumference. Moreover, in the blood of many of 



