104 



Even more delicate are the methods employed in the study of immunity. As 

 shown by the work of Meyer a and Uhlenhuth,& by means of the precipitin test the 

 presence and nature of proteins may be ascertained in a dilution of 1: 100,000. As is 

 well known, the chemical tests for albumin are of no value in dilutions over 1: 1,000, 

 and it is not specific. 



For the identification of some poisons and the standardization of certain drugs 

 of vast therapeutic application experiments on animals are practically the only 

 reliable method. 



There are no satisfactory chemical methods for the identification of the saponins, 

 but owing to their powerful hemolytic action and their effect on the heart and volun- 

 tary muscles their identification has become possible. According to Robert, <= picro- 

 toxin can be identified by experiments or animals only. The detection of curarin 

 by chemical tests is very unsatisfactory; by its action on the motor end organs, how- 

 ever, its identity can be established even when mere traces are present. Thus motor 

 paralysis in frogs has been induced by injecting 0.005 milligram of curarin. 



Adrenalin has been the subject of numerous investigations. On account of its 

 powerful action and its extensive therapeutic application, the strength of the various 

 preparations should be accurately known. A number of color tests have been pro- 

 posed for this purpose, some of which are of doubtful value and some may be employed 

 if properly controlled by tests on animals, which are very delicate. Meltzer and 

 Auer d have shown that a drop of a solution of 1: 120,000 dropped into the conjunctival 

 sac of a rabbit causes blanching of the conjunctiva and dilation of the pupil. Accord- 

 ing to Ehrmann, a reaction of the pupil of the excised eye of the frog may be obtained 

 with 0.000025 milligram of this drug. Similar results were obtained by other inves- 

 tigators who worked on the pharmacology of the drug. Cameron's / experiments with 

 this drug on rabbits have shown that 0.0003 milligram per kilogram will cause a rise 

 of blood pressure. 



Preparations of digitalis have been found to vary enormously in physiological 

 activity. Frankel Q states that the strength of the tincture varies from 200 to 400 

 per cent, and the infusion varies from 100 to 125 per cent. In a recent article 

 Lutzkaja' 1 states that the infusion of digitalis he examined was only 60 per cent of 

 the strength represented by the firm which prepared it. Barger and Shaw,*' in 

 England, examined nine tinctures of this drug, and found a variation of 75 per cent 

 in their strength. These authors made a comparative study of Keller's method and 

 the physiological test on an artificial infusion of digitalis made by adding a known 

 quantity of the drug to a mixture of hay and chaff. This was extracted with 60 per 

 cent alcohol. Chemical analysis of the extract showed the presence of 0.1 per cent 

 of digitalis, whereas the mixture contained 0.4 per cent. The same extract was 

 tested on frogs, however, and found to contain approximately 0.4 per cent. 



In the case of some drugs the physiological test above must be relied upon, no 

 chemical method having as yet been devised for their identification or quantitative 

 determination. Cannabis belongs to this category. Houghton and Hamilton, J in a 

 recent article, state that previous to the adoption of this test, preparations of the 



o Lancet, 1900 (2), p. 98. 



*>Deutsch. med. Wochenschr., 1900, 26: 734. 



c Loc. cit. 



dCentrbl. Physiol., 1904, 18: 317. 



Arch. exp. Path. Pharmak., 1905, 53: 97. 



/Proc. Roy. Soc. Edinburgh, 1905, 26: 161. 



^Ther. Gegenwart, N. S., 1902, 4: 112. 



^Arch. intern, pharmacodynamie, 1908, 18: 77. 



* Yearbook of Pharmacy, 1904, p. 541. 



J'Ther. Gazette, 1908,32: 26. 



