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BACTERIOLOGY, ANTISEPTICS AND DISEASE 



201 



2. By introducing living bacteria that have 

 been mad« much less virulent. 



Passive immunity may be introduced in the 

 following ways : 



1. By introducing dead bacteria into the 

 system. This has been done in immunising 

 people against typhoid, cholera and plague. The 

 chemicals contained in the dead microbes are 

 evidently the cause of immunity. 



2. By introducing bacterial chemicals secreted 

 by bacteria while living, as in the case of 

 diphtheria antitoxin. 



3. By introducing chemicals produced by 

 dead bacteria. 



4. By introducing bacteria or bacterial 

 chemicals (vaccines) that have nothing to do 

 with the production of the disease, as is done 

 in immunising animals against anthrax. 



790. Bacterial Vaccines. — A bacterial vaccine 

 is a liquid suspension of the killed culture of 

 bacteria or germs. These vaccines are prepared 

 in a bacteriological laboratory by growing, in 

 a suitable medium, the bacterial organism 

 associated with the particular disease. These 

 cultures are then killed at their minimum 

 thermal death point, after which the vaccine is 

 standardised according to dosage, and a very 

 small amount of preservative added to ensure 

 sterilisation of the product. Finally, the vaccine 

 is tested upon healthy guinea pigs. If these 

 remain well after injection, the vaccine is con- 

 sidered safe for use. 



The scientist Metchnikoff discovered that 

 when a germ entered the animal it caused a 

 local irritation that attracted large numbers of 

 white blood corpuscles to the part. These cells 

 are able to pass through the walls of the 

 blood vessels. They are antagonistic to the 

 invading germ, and, providing the germs 

 are not too numerous, will completely destroy 

 them. 



Professor Wright showed that the serum of 

 blood contained a substance which, in the pre- 

 sence of a germ, reacted upon the white cor- 

 puscle, making it more active. This action is 

 known as "opsonin" (Greek for "prepare for"). 

 He also demonstrated the value of the opsonic 

 index in determining the state of active im- 

 munity. He showed that when an emulsion of 

 killed bacteria was injected into the blood of an 

 animal suffering from the analogous disease, the 

 white corpuscles became very active and were 

 able to destroy three or four times as many 

 germs as they could previous to the animal 

 receiving the vaccine. 



Dr. T. C. Evans, B.V.S., of the Experimental 

 Laboratories at Ottawa, tells me of an instance 

 of a little girl who owned a small pony. The 

 pony contracted glanders and was destroyed. 

 The child developed a chronic infection which 

 resisted all medical treatment. A pure culture 

 of glanders was isolated from an ulcer in the 



2 A 



child's leg, and a bacterine was made from it. 

 After a few injections with it the case made a 

 complete recovery. Glanders is usually fatal in 

 the human being. 



The time is at hand when modern sanitation 

 and modern business will unite to sweep diseases 

 away and assist the laboratory-worker to bring 

 successful results from his hard labours in the 

 preparation of these bacterial vaccines. 



791. Of late a great number of new vaccines 

 have been made for the prevention and cure of 

 infectious diseases. One has been used for 

 several years for anthrax and black-leg. 



Dr. Evans has successfully made a vaccine 

 against that common disease strangles. Splendid 

 reports have been received regarding the im- 

 munisation and therapeutical treatment with this 

 vaccine. This vaccine has also been used with 

 great success in influenza. I have had occasion 

 to see the results of its use. Evans has treated 

 several cases of severe quittor in the horse by 

 preparing an autogenous vaccine from the germs 

 isolated in the actual case. 



There are many conditions where a vaccine 

 can be used in the scientific treatment of infected 

 wounds of the horse : for example, indolent 

 abscesses, infected nail pricks, fistulous withers, 

 poll evil, scratches, etc., and all wounds that are 

 slow in healing through bacterial infection. 

 Much useless pain from operations could thus be 

 avoided by the timely and judicious use of 

 bacterines. 



The Japanese scientist Hideyo Noguschi has 

 made some wonderful discoveries in quite 

 recent times. It was he who discovered the 

 real cause of tartar on the teeth, called gingiv- 

 itis, or, more properly, pyorrhoea alveolaris ; it 

 is a minute microbe. He also isolated the germ 

 of infantile paralysis and is preparing a vaccine 

 against it. {See Sec. 640.) He also showed that 

 the negri bodies are the real cause of rabies. 



Noguschi also isolated the germs that cause 

 locomotor ataxia (tabes dorsalis) and relapsing 

 or intermittent fever. Both of these are caused 

 by a minute bacterium, a spirillum. 



792. It will thus be seen that in reality a 

 pathogenic microbe has quite a number of 

 battles to fight before it can settle down quietly 

 in its host. 



Let us consider, for example, the journey of 

 a typhoid bacillus. The microbe gets into a 

 piece of food that is ready to be eaten through 

 the cook not being scrupulously clean. It passes 

 into the mouth and manages to escape all its 

 enemies, as mucus, saliva, etc., then passes into 

 the stomach ; but, on account of its being em- 

 bedded in some hard substance, it escapes the 

 hydrochloric acid in the stomach and also any 

 other of its enemies. It reaches the intestines, 

 where it has to fight against the mucous mem- 

 brane of the walls, and, after a great struggle, 

 gains access between two cells in a piece of tissue 



