DISTURBANCES OF METABOLISM, ETC. 159 



common. Hyaline change in the walls of arterioles may occur, 

 and in certain chronic conditions waxy change is brought about 

 in a similar manner. The latter has been produced in animals 

 by the repeated injection of the staphylococcus aureus. 

 Capillary haemorrhages are not uncommon, and are in many 

 cases due to an increased permeability of the vessel walls, aided 

 by changes in the blood plasma, as evidenced sometimes by 

 diminished coagulability. Similar haemorrhages may follow the 

 injection of some bacterial toxins, e.g. of diphtheria, and also of 

 vegetable poisons, e.g. ricin and abrin. Skin eruptions occurring 

 in the exanthemata are probably produced in the same way, 

 though in many of these diseases the causal organism has not 

 yet been isolated. We have, however, the important fact that 

 corresponding skin eruptions may be produced by poisoning with 

 certain drugs. In the nervous system degenerative changes 

 have been found in diphtheria, both in the spinal cord and in 

 the peripheral nerves, and have been reproduced experimentally 

 by the products of the diphtheria bacilli. There is also experi- 

 mental evidence that the bacillus coli communis and the strepto- 

 coccus pyogenes may, by means of their products, produce areas 

 of softening in the spinal cord, and this may furnish an explana- 

 tion of some of the lesions found clinically. It is also possible 

 that some serous inflammations may be produced in the same 

 way. 



B. Disturbances of Metabolism, etc. It will easily be 

 realised that such profound tissue changes as have been detailed 

 cannot occur without great interference with the normal bodily 

 metabolism. General malnutrition and cachexia are of common 

 occurrence, and it is a striking fact found by experiment that 

 after injection of bacterial products, e.g. of the diphtheria bacillus, 

 a marked loss of body weight often occurs which may be pro- 

 gressive, leading to the death of the animal. In bacterial 

 disease assimilation is often imperfect, for the digestive glands 

 are affected, it may be, by actual poisoning by bacterial products, 

 it may be by the occurrence of fever. The fatty degenerations 

 which are so common are indicative of a breaking down of the 

 proteid molecules, and are associated with increased urea produc- 

 tion, while the degeneration of the kidney epithelium renders 

 the excretion of waste products deficient or impossible, and this 

 is not infrequently the immediate cause of death. But of all 

 the changes in metabolism the most difficult to understand is 

 the occurrence of that interference with the heat-regulating 

 mechanism which results in fever. The degree and course of the 

 latter vary, sometimes conforming to a more or less definite type, 



