In addition to this there is very commonly in acute nephritis Haemorrhage from the Glomeruli. The blood which is usually present in the convoluted tubules comes from the glomeruli, and it is often possible, as in Fig. 426, to find glomeruli with blood inside the capsule as well as in neighbouring tubules.

Fig. 426. - Haemorrhage from a Malpighian tuft in a case of scarlet fever, a, tuft; b, blood between tuft and capsule; e, blood in viriniferous tubule extending from tuft, x 350.

Scarlatinal nephritis, whilst in most cases presenting the usual characters of parenchymatous nephritis, is sometimes characterized by such special changes in the glomeruli that the term Glomerulonephritis has been employed by Klebs to designate this and other forms in which the glomeruli are specially affected. In some cases of scarlatinal dropsy the kidneys are, to the naked eye, scarcely at all altered, although the patient may have died with symptoms of urremia. The glomeruli may be visible on section as red spots, and there may be evidences of hsemorrhage, but otherwise nothing abnormal. On microscopic examination, however, there are the marked changes in the glomeruli described above. These lesions must seriously interfere with the function of the tuft. Any accumulation within the capsule will compress the vessels and prevent the transudation of the water and other constituents. There may thus be a suppression of urine from glomerulonephritis.

Besides these, which are the results of the specific poison of scarleffever., there is a form of nephritis which is apparently to be referred to the absorption of septic matter from the lesion in the throat. It is not that the microbes themselves are carried to the kidney, but that probably their toxine in the process of excretion leads to what may be called a Septic nephritis. The kidney is greatly enlarged and pale. In a case observed by the author, in which the patient died in the ninth day from the onset of the fever, the microscopic appearances were such as are shown in Fig. 427. There was a general infiltration of leucocytes, which occupied the glomeruli and extended to the cortex generally. (See further in papers by Crooke).

The interstitial tissue in subacute and chronic cases of parenchymatous nephritis shows marked changes. Even in the acute stage there may be considerable infiltration with leucocytes. As the inflammation is prolonged, however, there is new-formation of connective tissue and that special thickening of the capsule of the glomerulus, which is a prominent feature in interstitial nephritis. As this process goes on it produces distortion of the secreting tissue and irregularity of the surface of the kidney.

Fig. 427. - Glomerulo-nephritis from a case of scarlet fever. The Malpighian tuft in the middle of the figure is crowded with round cells, which are also present very abundantly in the interstitial substance between the tubules, whose epithelium is granular, x 300.

The Naked-Eye Appearances In Parenchymatous Nephritis

If the inflammation be mainly glomerular the general appearance of the kidney may be little altered (see above).

As a general rule in acute nephritis the organ is found enlarged, and it may be more than twice its normal size. The capsule is easily removed and the surface of the organ has a generally reddish colour from injection of the vessels. Small red or brown areas are generally visible on close inspection of the surface, these being from haemorrhages into the tubules. There are also usually opaque yellow patches, from fatty degeneration of the epithelium. On section the cortex is seen to be swollen and thicker than normal, and the haemorrhages and fatty tubules will be visible as minute red and yellow markings. The latter especially produce a marked mottling of the cut surface in the cortex, and there are often elongated yellow streaks from fat in the straight tubules. The cortex, however, is usually pale as a whole as compared with the pyramids.

The Large white kidney is a further stage of parenchymatous nephritis. It represents a certain prolongation of the condition with partial subsidence of the inflammation into a subacute stage. The patient has been subject for months or years to intermitting attacks of dropsy with scanty albuminous urine. The kidney is large, and on the surface has a generally pale appearance, with little or no irregularity. The capsule is non-adherent. On section the cortex is seen to be bulky and pale. On close examination of the surface and of the cortex it is seen that, besides the general paleness, there is an opaque mottling, representing a fatty condition of the epithelium. In the large white kidney the glomeruli and tubules show the changes described above, the glomeruli especially often showing great accumulation of epithelium inside the capsule. In addition there is considerable interstitial new formation of connective tissue, and, commonly, some sclerosis of the glomeruli.

It is proper to mention that the naked-eye appearances of the large white kidney may be imitated by amyloid disease, where there is also usually some fatty mottling, and by septic nephritis, where there is a general infiltration of leucocytes.

The contracted fatty kidney represents the latest stages of parenchymatous nephritis. The organ may be greatly reduced in size, so as to weigh only 2 or 2 1/2 ounces. It is somewhat irregular on the surface, but the appearance is rather of smooth rounded elevations than of granulations. The kidney is soft and flabby in consistence, and the capsule is usually non-adherent. It is generally pale and presents in addition a well-marked fatty mottling in the cortex and on the surface. The shrinking here is chiefly in the cortex, which may be very thin. The tubules are partly atrophied but partly dilated, and in the latter case their epithelium is usually fatty. ■ The shrinking of the tissue brings the glomeruli close together and they often show marked sclerosis.