562 IMMUNITY 



power in a dry condition, preserved in a vacuum in a cool place, 

 and in the absence of light. A thoroughly dry condition is 

 ensured by having the glass bulb containing the dried serum 

 connected with another bulb containing anhydrous phosphoric 

 acid. With such a standard test-serum any newly prepared 

 serum can readily be compared. 



Roux has adopted a standard which represents the animal weight in 

 grammes protected by 1 c.c. of serum against the dose of virulent bacilli 

 lethal to a control guinea-pig in thirty hours, the serum being injected 

 twelve hours previously. Thus, if '01 c.c. of a serum will protect a 

 guinea-pig of 500 grins, against the lethal dose, 1 c.c. (1 grm.) will pro- 

 tect 50,000 grms. of guinea-pig, and the value of the serum will be 50,000. 



Use of Antitoxic Sera, In all cases the antitoxic serum ought 

 to be injected as early in the disease as possible, and in large 

 doses. In the case of diphtheria 1500 immunity units of anti- 

 toxic serum was the amount first recommended for the treatment 

 of a bad case, but the advisability of using larger doses has 

 gradually become more and more evident. Sidney Martin 

 recommends that as much as 4000 units should be administered 

 at once, and that if necessary this quantity should be repeated. 

 A strong serum prepared by Behring contains 3000 units in 

 5 to 6 c.c., but even stronger sera may be obtained. Even very 

 large doses of antitoxic serum are without any harmful effects 

 beyond the occasional production of urticarial and erythematous 

 rashes (p. 601). Where large quantities of serum require to be 

 administered, as is always the case with antitetanic serum, in- 

 jections must be made at different parts of the body ; preferably 

 not more than 20 c.c. should be injected at one place. In recent 

 times intravenous injection has been introduced, the advantage 

 being greater rapidity of action. The immunity conferred by 

 injection of antitoxic serum lasts a comparatively short time, 

 usually a few weeks at longest. 



Sera of Animals immunised against Vegetable and Animal 

 Poisons. It was found by Ehrlich in the case of the vegetable 

 toxins, ricin and abrin, and also by Calmette and Fraser in the 

 case of the snake poisons, that the serum of animals immunised 

 against these respective substances had a protective effect when 

 injected along with them into other animals. Ehrlich found, 

 for example, that the serum of a mouse which had been highly 

 immunised against ricin by feeding as described above, could 

 protect another mouse against forty times the fatal dose of that 

 substance. He considered that in the case of the two poisons, 

 antagonistic substances "anti-ricin" and "anti-abrin" were 



