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THEORY AND PRACTICE OF MEDICINE.
Fig. 4.
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Fatty degeneration of double- borderednerve fibres in the peripheral part of a divided cerebro-spinal nerve, a. After three days have elapsed; b. After a fortnight ; c. After three weeks ; d. After two months, (Rindfleisch).
g-lobules" or "exudation-corpuscles," as well as pus-corpuscles, are merely the re- sult of the conversion of the contents of cells, either normal to the part or which have mig-rated from the blood, into granular fat. A certain number of these originate in cel- lular-tissue corpuscles. In the epithelium of the renal tubes, as well as in the cells of the liver, supra-renal capsules, and lympha- tic glands, fatty degeneration also occurs ; while the "arcus senilis" is due to the same process in the cells of the cornea. Most organs in their natural decay under- go this chang-e, and it is further exempli- fied in the formation of many secretions; in the production of the corpus luteum in the ovary ; and in the deg"enerative changes which the placenta undergoes on the ap- proach of the full period of preg"nancy. Morbid growths, such as cancer, tuber- cle, and various tumours, are likewise sub- ject to fatty metamorphosis.
When cells undergo fatty degeneration, they often enlarge and become more spherical and distended. The granules first appear at a distance from the nucleus, scattered irregularly ; they then increase in number and size, obscure the nucleus, and finally render it quite invisible. The cell-wall is often ruptured or absorbed, leaving merely an accumulation of granular fat, which frequently separates into its constituent particles, owing to intermediate liquefaction.
Caseation; Caseous or Cheesy Degeneration. — These terms have come into considerable prominence of late years, and are used to signify the conversion of various structures into a kind of soft, dryish, cheesy-looking substance, of yellowish-colour. It is really a process of partial fatty degeneration with drying, and the material formed is found to consist of withered cells, fat-granules, partially saponified fat, and crystals of cholesterin. Caseation generally occurs in connection with some morbid product, or where ihere is a great accumulation of cells pressing closely upon each other, and it is especially met with where vessels are few, so that the tissue is dry. Pulmonary phthisis affords some of the most fre- quent examples of caseous degeneration, but by no means of neces- sity associated with tubercle. It is also often seen in scrofulous lymphatic glands, cancer, and chronic abscesses. Ultimately a more or less creamy or puriform-looking fluid substance may be produced, or a kind of fatty emulsion, which may be completely removed by absorption or in other ways ; or it may become encap- suled by some dense tissue and finally calcify. Many pathologists regard caseous material as a morbid poison, which, after absorp- tion into the blood, is capable of originating tubercle by an infec- tive process.
