HAEMOLYSIS AND IMMUNITY 107 



Bacterial Haemolysins. Certain pathogenic bacteria e.g., Bacillus pyocyaneus 

 and staphylococcus (the organism of boils) produce agglutinins for human corpuscles. 

 Sometimes these play a part in the formation of emboli. The corpuscles may b3 

 clumped together, mixed with the infecting bacteria, and carried by the circulation 

 to another part and so spread the mischief. Haemolysis occurs in the blood during 

 an attack of blood-poisoning (septicaemia). The best-known bacterial haemolysins are 

 those produced by the bacteria of tetanus (lockjaw) and of typhoid, and the staphy- 

 lococcus and streptococcus. They are known as tetano-lysin, typho-lysin, etc. 

 Their action is due to direct combination with the cell without the aid of an inter- 

 mediary (amboceptor). They are therefore comparable to toxins, which unite directly 

 with the red corpuscles and destroy them. 



Haemolysis produced by Vegetable Poisons. Some vegetable poisons, crotin 

 (croton-oil seed) and phalein (Phallus impudieat, a fungus), have a very marked 

 haemolytic action, and others, ricin (castor-oil bean) and abrin (jequirity bean), agglu- 

 tinate, but produce little haemolysis. Immunity can be established against these 

 bodies and antibodies produced. Against another group of vegetable poisons no 

 antibodies are produced. In this are included saponin, cyclanin from cyclamen, 

 solanin from the green potato, helvellic acid from a species of mushroom (Hdvdla 

 esculenta). Saponin produces haemolysis in 1 : 100,000. These poisons differ alto- 

 gether from bacterial toxins, being resistant to heat, and having no resemblance to 

 proteins. They are related to glucosides. The action of saponin is prevented by 

 the presence of an excess of cholesterin in the blood ; haemolysis is probably caused 

 by the cholesterin portion of the stroma linking the poison to the corpuscles. The 

 toxicity of these substances is not in any way proportional to their haemolytic 

 powers, their chief effect being paralysis of the heart and injury to the central 

 nervous system. 



Haemolysis by Snake Venoms. The salivary secretion of certain snakes cobra, 

 rattlesnake, copperhead causes agglutination of the red corpuscles, and in some 

 cases also induces haemolysis. The snakes secrete in their saliva an amboceptor, and 

 the person bitten provides the complement. An animal can be immunized against 

 snake venom so that it comes to withstand many times the lethal dose. An " anti- 

 venin " is produced which, by linking on to the amboceptor in the snake venom, pre- 

 vents its union with the red corpuscle. 



The hsemolysins can be dried at a cool temperature without losing potency, are 

 destroyed by acids and alkalies, and inhibited in their action by salts. Introduced 

 by the stomach they have no action. In health but little haemolysis takes place apart 

 from the destruction of effete corpuscles. In fevers haemolysis may be produced 

 by bacterial toxins. It is suggested that certain anaemias may be due to haemolysins 

 formed by parasitic inhabitants of the alimentary tract. If more than a small amount 

 of haemoglobin is set free in solution in the plasma, it escapes in the urine, giving rise 

 to the condition known as hsemoglobinuria. In some rare cases haemoglobinuria 

 follows exposure to cold e.g., it occurs in some persons after putting the hands in 

 iced water. 



Immunity. Besides the substances which can be isolated by 

 chemical means, weighed, and analyzed, there are many and subtle 

 properties possessed by the plasma, such as its immunizing powers, 

 which can only be detected by the newly-discovered biological tests. 

 These tests depend on the reaction of living substances, and are of 

 the most extraordinary delicacy. On these properties of the plasma 

 depend the immunity of the organism against infective diseases and 

 certain toxins of animal or vegetable origin. The immunizing sub- 

 stances are quite specific for each bacterium or toxin. It is known 

 that man is immune to certain infective diseases which affect other 

 animals. For example, he is immune to swine fever. This is termed 

 natural immunity. It is also known that a second attack of whooping- 

 cough, measles, smallpox, etc., is rare. He who has suffered once 

 has an acquired immunity. Such acquired immunity may be estab- 



