490 METABOLISM OF THE TISSUES. 



drops of fat within the fat-cells of the pauniculus and around the viscera, as well 

 as in the marrow of bone (but they are never deposited in the subcutaneous tissue 

 of the eyelids, of the penis, of the red part of the lips, in the ears and nose). 

 This is quite different from the fatty atrophy or fatty degeneration which 

 occurs in the form of fatty globules or granules in albuminous tissues e.g., in 

 muscular fibres (heart), gland-cells (liver, kidney), cartilage-cells, lymph- and 

 pus-corpuscles, as well as in nerve-fibres separated from their nerve-centres 

 The fat in these cases is derived from albumin, much in the same way as fat is 

 formed in the gland-cells of the mammary and sebaceous glands. Marked fatty 

 degeneration not unfrequently occurs after severe fevers, and after artificial heating 

 of the tissues; wben a too small amount of is supplied to the tissues, as occiirs in 

 cases of phosphorus poisoning (Bauer); in drunkards; after poisoning with arsenic 

 and other substances; and after some disturbances of the circulation and inner- 

 vation. Some organs are especially prone to undergo fatty degeneration during the 

 course of certain diseases. 



243. The Metabolism of the Tissues, 



The blood-stream is the chief medium whereby new material is 

 supplied to the tissues and the effete products removed from them. 

 The lymph which passes through the thin capillaries, comes into actual 

 contact with the tissue elements. Those tissues which are devoid 

 of blood-vessels in their own substance, such as the cornea and 

 cartilage, receive nutrient fluid or lymph from the adjacent capillaries, 

 by means of their cellular elements which act as juice-conducting 

 media. Hence, when the normal circulation is interfered with, as 

 by atheroma or calcification of the walls of the blood-vessels, these 

 tissues are secondarily affected [this, for example, is the case in arcus 

 senilis of the cornea, due to a fatty degeneration of the corneal 

 tissue, owing to some affection of the blood-vessels on which the 

 cornea depends for its nutrition]. Total compression or ligature 

 of all the blood-vessels, results in necrosis of the parts supplied by 

 the ligatured blood-vessels. 



Hence, there must be a double current of the tissue juices ; the 

 afferent or supply current, which supplies the new material, and the 

 efferent stream which removes the effete products. The former brings 

 to the tissues the proteids, fats, carbohydrates and salts from which 

 the tissues are formed. That such a current exists is proved by 

 injecting an indifferent, easily recognisable substance into the blood, 

 e.g., potassium ferrocyanide, when its presence may be detected in 

 the tissues, to which it has been carried by the out-going current. 

 The efferent stream carries away the decomposition products from 

 the various tissues, more especially urea, C0 2 , H 2 and salts, and 

 these are transferred as quickly as possible to the organs through 

 which they are excreted. That such a current exists is proved by 

 injecting such a substance as potassium ferrocyanide into the tissues, 



