74 IMMEDIATE PRINCIPLES OF THE TISSUES. 



fatty acids, each of which may be found in a state of isolation from 

 other fatty elements. 



Though several of the tissues contain the fat-globules under con- 

 sideration, they are most abundant in the corpus luteum. They 

 also abound in cancerous (encephaloid), atheromatous, and other 

 morbid growths ; and when they replace the normal tissues in or- 

 gans, or become abnormally abundant in them, they produce the 

 "fatty degeneration," or Stearosis, and in this way may produce 

 fatal results. The organs most liable to this change will be speci- 

 fied in the chapter on "Adipose Tissue." 



The fat-globules exist in the fluids in a state of suspension or 

 emulsion. The sniallest of all are those of the chyle. They are 

 twice or thrice as large in the blood during digestion, and are still 

 larger in milk, constituting the cream. Fat-globules also normally 

 exist in urine, semen, prostatic fluid, saliva, nasal mucus, synovia, 

 and bile, and in the serosity of the pleura, of the peritoneum, and 

 that produced by a blister. Blood-serum contains fat even when 

 mixed with other fluids (as urine), and pus also contains it in 

 notable amount. 



The fatty immediate principles exist in the ovum, and through life. 

 In the adult they constitute about 5 per cent., or ^ of the weight 

 of the body. Of the entire brain, fat constitutes at least 10 per cent. ; 

 of the muscles, 1 J to 4 per cent. ; and of the blood, 0.14 to 0.33 

 per cent. The globules alone of the blood contain 0.331 per cent. ; 

 the serum alone, 0.175 ; and the fibrine (when dry), 2.6 per cent. 



Origin. The fatty principles in the body are mostly taken into 

 the organism, already formed, in the food, and, being converted into 

 an emulsion in the duodenum and jejunum by the action of the 

 pancreatic fluid (Bernard), are then absorbed mainly by the lacteal s, 

 and enter the venous current from the thoracic duct. But it is also 

 extremely probable that the fatty principles may be, to some extent, 

 formed in the human organism; and Liebig's idea that they are 

 formed in the alimentary canal, from the metamorphosis of certain 

 nitrogenized elements in our food, is the most plausible. At least, 

 the amount of fat in the blood does not vary much, whether the food 

 contains very much fat, or is deficient in it (Boussingaulf) ; and both 

 the amylaceous and the nitrogenized compounds in our food cer- 

 tainly afford the elements for the formation of the fatty principles. 

 The fact sometimes cited to prove that carnivorous animals form 

 fat within their own organisms viz., that their milk contains fat 



