28 FATTY DEGENERATION. 



deposits is far less common. On the contrary, an increase in 

 density, a true petrifaction, often ensues, especially in cheesy 

 lymphatic glands, owing to a deposition of calcareous salts in 

 their interior. 



§ 35. In conclusion, let us glance at the causation and the 

 distribution of fatty metamorphosis. In the foregoing para- 

 graphs we have often had occasion to touch on these points ; 

 now, therefore, we may content ourselves with a general review. 



First, then, we may regard fatty transformation as being a 

 regular mode of the retrograde metamorphosis of many tissues 

 which are subject to rapid nutritive change. Among these, the 

 epithelial structures naturally take a leading place. If we 

 moisten the surface of any serous membrane and scrape it with 

 a scalpel, the fluid we obtain will seldom fail to exhibit a certain 

 number of epithelial cells which have undergone fatty degenera- 

 tion, side by side with others which are perfectly normal. 



The epithelium of the mammary and sebaceous glands is 

 peculiarly liable to undergo fatty metamorphosis in the ordinary 

 course of events ; so also that of the lungs, and the renal epi- 

 thelium of dogs and cats. Whether the white blood corpuscles, 

 on completion of their span of life, finally succumb to fatty 

 degeneration, is a question which must be left open; it is an 

 undoubted fact that a certain number of granule cells are con- 

 stantly met with in the iDlood of amphibia ; but these may of 

 course have originated in the epithelial lining of the vessels. 



The fatty metamorphosis which forms an element in senile 

 decay is intimately connected with the above varieties. The 

 €nfeeblement of nutrition due to old age is especially manifested 

 in parts where arrangements for the transport of nutrient 

 matter are most complicated by nature, and in a certain sense 

 most difficult. 



I allude, of course, to those great tracts of non-vascular tissue 

 which occur in cartilaginous organs, and the transparent media 

 of the eye. Hence it is that we so often find the cells of the 

 laryngeal and tracheal cartilages in old people in a state of fatty 

 degeneration, the capsules being occupied by one or more oil 

 globules. To this group also belongs the arcus senilis, a fatty 

 degeneration of the corneal corpuscles adjoining the sclero-cor- 

 neal junction, and the gerontoxon lentis, an opacity situated at the 

 junction of the posterior surface of the nucleus of the crystalline 



