184 RELATIONS OF BACTERIA TO DISEASE 



(2) General Lesions produced by Toxins. — In the various in- 

 fective conditions produced by bacteria, changes commonly 

 occur in certain organs unassociated with the presence of the 

 bacteria ; these are produced by the action of bacterial products 

 circulating in the blood. Many such lesions can be produced 

 experimentally. The secreting cells of various organs, especially 

 the kidney and liver, are specially liable to change of this kind. 

 Cloudy ' swelling, which may be followed by fatty change or 

 by actual necrosis with granular disintegration, is common. 

 Hyaline change in the walls of arterioles may occur, and in 

 certain chronic conditions amyloid change is brought about in 

 a similar manner. The latter has been produced in animals 

 by repeated injections 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 corre- 

 sponding 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. It is probable that 

 some of the lesions of the nervous system occurring in syphilis 

 have likewise a toxic origin. Besides the effects on tissues 

 enumerated, more subtle changes, e.g., those observed in the 

 reaction and coagulability of the blood, are also probably trace- 

 able to toxic effects. 



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 progressive, 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, and excretion is interfered with 

 by the damage done to the excretory cells. But of all the changes 



