234 THE PRINCIPLES OF IMMUNOLOGY 



the beginning of the hay-fever season, which disappeared for a few 

 weeks after specific desensitization. On the other hand, numerous 

 other investigators have failed to demonstrate such reactions, and this 

 phase of the question must be considered unsettled. Dunbar claimed 

 that treatment with the anti serum " pollantin " produced specific effects, 

 but Weichardt maintains that equally good results are obtained with 

 the serum of normal animals taken in the summer season. Cooke, 

 Flood and Coca were unable to demonstrate immune reactions in the 

 sera of rabbits inoculated repeatedly with the pollens of ragweed and 

 of redtop. Other objections to the toxin conception include the fact 

 that the majority of normal individuals are, practically speaking, abso- 

 lutely resistant to the pollens and fail to react to doses 1000 times the 

 dose which produces reactions in susceptible cases. This is not in 

 accord with the finding in regard to any other of the known toxins. 

 Apparently normal individuals may resist diphtheria toxin, but Cooke 

 and Van der Veer have pointed out that such resistance depends upon 

 the presence of demonstrable antitoxin, which is not true in resistance 

 to pollens. By mixing the " pollantin " and pollens and then testing 

 by an ophthalmic reaction in sensitive individuals Dunbar's assistant, 

 Prausnitz, plotted a curve of neutralization, but Wolff-Eisner found 

 that this curve does not follow the law of multiple proportions and is 

 therefore not similar to other toxin-antitoxin combinations. There 

 seems, therefore, little ground for assuming that the pollens contain 

 a special toxin and the subsequent work with hay fever and similar 

 conditions indicates that they represent a condition of hypersuscepti- 

 bility to proteins or to protein decomposition products. 



Technic of Cutaneous Tests. If the antigenic proteins are already in 

 solution, as is the case with blood serum, no especial treatment is required 

 other than suitable dilution under strictly aseptic precautions. If the protein 

 is in solid form, as in the case of vegetable proteins and other cellular forms, 

 extracts are required. The studies of Walker and of Wodehouse on the 

 preparation of materials for the tests have been of the utmost importance. 

 These are independent of the preparation of the various tuberculins, which 

 will be discussed subsequently. They found that an excellent dried prepara- 

 tion of serum could be obtained by precipitating with several volumes of 

 acetone, washing the precipitate centrifugally twice with alcohol and with 

 ether, and drying to a powder. The powder may be applied to an incision in 

 the skin and dissolved with N/io NaOH solution. Bacteria are cultivated on 

 solid media, washed centrifugally in salt solution, then twice in absolute alcohol 

 with 0.5 per cent, phenol added, twice in ether and then dried to a powder, which 

 may be used as is the serum powder. Cereals, nuts and other seeds, roots 

 and tubers, fruits, leaves and stems are extracted in water, precipitated with 

 95 per cent, alcohol, washed with 95 per cent, alcohol, absolute alcohol, ether 

 and desiccated over hydrochloric acid. Hair and dandruff of animals may 

 be employed as a dissolved extract in 14 per cent, alcohol, but for more 

 accurate studies, dried preparations of acid metaprotein, alkali metaprotein 

 and pepton extracted from the material are employed. 



The methods of inoculation include introduction of the protein into 

 abraded surfaces and intracutaneous injection through a fine needle. In 

 special instances, as, for example, in the use of tuberculin, the material may 

 be incorporated in an ointment and carefully rubbed into the skin; this is 

 the so-called percutaneous test. Somewhat similar to the cutaneous tests is 

 the ophthalmo-reaction, more particularly applied in tuberculin tests, where 

 the material is instilled into the opnjunctival sac. Subcutaneous injection of 

 material is also resorted to, again with tuberculin rather than with other 



