666 



APPENDIX. 



FIG. 375. 



EXAMINATION OF THE VASCULAR AND ABSORBENT SYSTEMS. 



Vessels. The examination of the minute vessels requires but 

 little previous preparation. A piece of the pia mater, or the mesen- 

 tery of a young child, or a small artery from which the cerebral 

 neurine has been gently washed, may be placed for this purpose 

 under the microscope. The epithelial cells of the lining mem- 

 brane, and the contractile fibre-cells may be rendered distinct by 

 the addition of acetic acid. To demonstrate the fibre-cells of 

 the contractile coat, Dr. Beale recommends that an artery of 

 moderate size, and not quite fresh, be slit up, and its lining 

 membrane removed by careful scraping; the subjacent elastic 

 tissue is then to be removed and torn to pieces with fine needles, 



and finally placed upon a glass slide and 

 moistened with a few drops of water. 

 The spindle-shaped or muscular fibre- 

 cells are readily obtained from the renal 

 veins. 



It is highly important that the student 

 should make himself well acquainted 

 with the healthy appearance of the mi- 

 nute arteries of the brain, since they suf- 

 fer remarkable changes in disease. In 

 white softening of the brain, they un- 

 dergo a sort of fatty degeneration, nu- 

 merous minute oil-globules being aggre- 

 gated together at short intervals along 

 their walls. These oily masses are readily 

 detected by their high refracting power. 

 (Fig!> 375.) 



The vessels of the kidney are also, 



from the changes they suffer in disease, worthy of especial inves- 

 tigation. To prepare them for examination it is only necessary 

 to wash out from a thin section the epithelium of the renal tubes, 

 and add a few drops of acetic acid to render them more distinct. 

 The distinct arrangement of the nuclei of the circular and longi- 

 tudinal fibres, and the greater thickness of their walls, will serve 

 to distinguish the arteries from the veins. The coats of the 

 latter are very thin. 



Thickening of the arterial coats of the corpora Malpighiana 

 is well seen, according to Dr. Johnson, in the small, contracted 

 drunkard's kidney. 1 The normal thickness of the Malpighian 

 artery is about one-fifth or one- sixth the diameter of the vessel; 

 in this disease it is increased to one-third. 



Some observers have thought that they detected epithelial cells 

 upon the external surface of the Malpighian vessels ; but the 

 researches of Mr. Bowman negative this opinion. 



1 Diseases of the Kidneys. 



