1 86 PHYSIOLOGY OF NUTRITION 



that have been previously immunized by vaccination. This method of treat- 

 ment of diseases is called serumtherapy. 



In many cases the pathogenic bacteria are distributed throughout the whole 

 body of the infected animal or human being; in other cases they are localized 

 in some special region. The bacilli of diphtheria and tetanus are thus local- 

 ized. In such cases the injurious action of the bacteria is manifestly not directly 

 due to their number but to their poisonous excretions. Although diphtheria 

 bacilli develop only in the throats of human beings, nevertheless the entire 

 body is poisoned by the toxins excreted by the bacterial cells. Diphtheria 

 toxin may be obtained from bouillon cultures of the diphtheria bacillus by filter- 

 ing the liquid through a Chamberland filter, the filtrate being very poisonous. 

 Tetanus bacilli are present in many soils. If a wound is infected with tetanus, the 

 bacteria develop only in the immediate neighborhood of the lesion but, even so, 

 the disease is deadly, since tetanus toxin is extraordinarily poisonous. One gram 

 of this toxin is capable of bringing about the death, by poisoning, of 75,000 men. 



§8. Lipoids and Phosphatides.- — The term "lipoid," which was introduced 

 by Overton, 1 may be understood to include 2 all tissue and cell constituents that 

 may be extracted by ether and similar solvents. Here belong not only fats 

 and fatty acids but also various other substances, among which cholesterin and 

 complex phosphatides are especially important. Thudichum 3 designates as 

 phosphatides those organic compounds containing phosphorus, that are soluble 

 in alcohol and ether. These substances are very unstable and are chemically 

 very active; they constitute an indispensable part of the protoplasm of all living 

 cells. Many complex phosphatides undergo auto-oxidation. 



Recent investigation shows that phosphorus is not the only mineral sub- 

 stance contained in lipoids. Thus, Glikin 4 found that half of the total iron 

 content of human and cow's milk is contained in lipoids. Winterstein and 

 Stegmann 5 have found, in the leaves of Ricinus (castor bean), a phosphatide that 

 contains 6.74 per cent, of calcium. Phosphatides containing carbohydrates are 

 present in some plants. 6 It may be suggested that lipoids form combinations 



J Overton, Ernst, Studien iiber die Narkose, zugleich ein Beitrag zur allgemeinen Pharmakologie. 

 Jena, iooi. 



2 Bang, Ivar, Biochemie der Zellipoide. Ergeb. Physiol. 6: 131-186. 1907. 



3 Thudichum, John L. W., Die chemische ^Constitution des Gehirns des Menschen und der Tiere. Tu- 

 bingen, IOOI. 



4 Glikin, W., Zur biologischen Bedeutung des Lecithins. III. Mitteilung. Ueber den Lecithin- und 

 Eisengehalt in der Kuh- und Frauenmilch. Biochem. Zeitsch. 21 : 348-354. 1909. 



6 Winterstein, E., and Stegmann, L., Ueber einen eigenartigen phosphorhaltigen Bestandteil der Blatter 

 von Ricinus. VI. Mitteilung. Ueber Phosphatide. Zeitsch. physiol. Chem. 58: 527-528. 1908-1909- 



6 Hiestand, O., Historische Entwickelung unserer Kenntnisse iiber die Phosphatide. Beitrage zur 

 Kenntnis der pflanzlichen Phosphatide. Zurich, 1906.* Winterstein, E., and Hiestand, O., Beitrage zur 

 Kenntnis der pflanzlichen Phosphatide. II. Mitteilung. Zeitsch. physiol. Chem. 54: 288-330. 1907-08. 

 Winterstein, E., Beitrage zur Kenntnis pflanzlicher Phosphatide. III. Mitteilung. Ibid. 58: 500-505. 

 1908-09. Winterstein, E., and Smolenski, K., Beitrage zur Kenntnis der aus Cerealien darstellbaren Phos- 

 phatide. IV. Mitteilung. Ueber Phosphatide. Ibid. 58: 506-521. 1909. Smolenski, K., Zur Kenntnis 

 der aus Weizenkeimen darstellbaren Phosphatide. V. Mitteilung. Ueber Phosphatide. Ibid. 58: 522-526. 

 1908-09. 



8 For a recent discussion of these substances see: Rosenbloom, Jacob, and Gies, W. J., A 

 proposed chemical classification of the lipins, with a note on the intimate relation between 

 cholesterols and bile salts. Biochem. bull. 1: 51-56. 1911. Rosenbloom, J., Intracellular 

 lipins. Ibid. 1: 75-79. 191 2. — Ed. 



