472 THE SOLIDS. 



rently due to the peculiar refraction of light by the thickened mem- 

 brane). The nuclei are obscured or invisible, owing to the thickness of 

 the intervening wall, but nevertheless exist in considerable numbers. 

 The Malpighian bodies and capillaries are usually obliterated. The 

 kidney has in fact become, like the tumours whose structure it resembles, 

 a true non- vascular texture. 



" The explanation of the peculiar extension of the pyramidal striae 

 towards the surface in these cases, is to be found in the fact, that even in 

 the normal condition the convoluted tubuli have a general disposition 

 from the bases of the pyramids towards the surface, in the direction of 

 the striae of the cones. This is evident from the facility with which the 

 gland tears in that direction ; although in the normal state this dispo- 

 sition is masked by that of the vessels, which, passing in strait lines 

 through the cones, break into a complicated network of capillaries at 

 the bases of the pyramids. In the present lesion, the vessels having dis- 

 appeared, and the course of tubes being strongly marked, their disposi- 

 tion towards the surface becomes manifest, and the abrupt line of 

 demarcation between the cortical and pyramidal substance, caused by 

 the presence of the vessels, is obliterated." 



CONCLUSION. 



WITH the view of enabling the reader to place the foregoing observa- 

 tions in relation with the descriptions found in systematic pathological 

 works, Dr. Gairdner subjoins the following short remarks on the principal 

 physical characters usually ascribed to diseased kidneys. 



" Increase of Size and Weight : Hypertrophy. Enlargement of the 

 kidney occurs chiefly in consequence of three conditions : 1st. from 

 sanguineous engorgement ; 2d. from distention of the tubes by secretion 

 or exudation ; 3d. from permanent dilatation and thickening of the tubes. 

 Of all these causes, the second is by far the most common. The last is 

 characteristic of the waxy degeneration formerly described. 



" The quantity of liquid in the tubes is, at all times, subject to so much 

 variation, that it is difficult to say what amount of increase of weight 

 may be thereby occasioned without the existence of any positively morbid 

 condition. It is not very uncommon to find kidneys otherwise not differ- 

 ing from the healthy standard, about double the usual weight, or between 

 seven and eight ounces each. I have more than once found them to 

 weigh nine ounces each, with very slight marks of disease. When the 

 weight much exceeds this, it is probable it arises from the rare combina- 

 tion of vascular and tubular engorgement. 



"In kidneys containing oleo-albuminous exudation, the greatest increase 

 of size is attained, when the exudation is universal, and unaccompanied 

 by desquamation. 



