176* GENERAL PHYSIOLOGY 



typhoid fever. The chemical composition of these substances has 

 become somewhat better known recently, especially through the 

 comprehensive and exhaustive labours of Brieger ('85-'86). Some 

 of them, the ptomaines that were first found, which are produced 

 by the putrefaction of proteid substances through the metabolism 

 of the putrefactive bacteria, as in dead bodies, are nitrogenous 

 bases that are related to the so-called alkaloids or vegetable bases, 

 which arise in the plant-body and likewise represent very 

 poisonous excretory substances. 



Finally, we may refer here briefly to a very interesting series of 

 substances which are produced, likewise, by the metabolism of 

 bacteria chiefly, but also of very many other cells, and very 

 recently have attracted the attention of investigators. These are 

 the toxalbumins, poisonous proteids, which are produced in the 

 metabolism of the cells by transformation from other bodies, and 

 in the pathology of infectious diseases play an important role. 

 Most of these toxalbumins are globulins and albumoses. Thus, 

 the active constituent of tuberculin, which was obtained some 

 time ago by Koch from the metabolic products of tubercle 

 bacilli, is a toxalbumose, which in small doses is extremely 

 poisonous. By the production of another toxalbumose the bacilli 

 of diphtheria cause very characteristic phenomena of poisoning in 

 the bodies of persons ill with diphtheria, the phenomena dis- 

 appearing very slowly. The toxalbumose of the bacteria of 

 diphtheria was the first toxalbumin which was recognised as such ; 

 it was so recognised by LofHer ('90), and was obtained pure by 

 Brieger and Frankel ('90). No little astonishment was caused 

 when the first poisonous proteids were recognised, since the proteids 

 had been known so long as harmless substances, and even as abso- 

 lutely necessary food-substances. And the surprise was no less 

 when later it was found that the poisonous effects of snake-bites, 

 which are so greatly feared, and of the blood of many fishes, such 

 as the lamprey, are to be traced, likewise, to the poison of such 

 toxalbumins, which are produced by the metabolism of the tissue- 

 cells and are excreted. 



Solid excretions are found almost exclusively in cells that take in 

 solid food. In them the indigestible residue of the food is given 

 off to the outside in the form of solid excretions in the manner 

 already described. In a few cases the excretory substances which 

 occur dissolved in the cell-contents are formed into solid con- 

 cretions within the cell and are then cast out ; this is the case 

 in the ciliate Infusoria, according to the investigations of Rhumbler 

 ('88). At present it is not yet decided whether the concretions of 

 yuanin and the crystals of calcium guanin which accumulate in many 

 cells and are stored permanently in the protoplasm, such as in the 

 beautifully iridescent crystalline plates and needles in the 

 epidermis-cells of amphibians and fishes, are to be regarded as 



