BIOLOGICAL EXAMINATION 135 



In the course of ten minutes this mixture is converted into a gluey or pasty mass 

 The mass in the test tube is then heated to a temperature not exceeding 86° F. and 

 a 50 percent solution of sulphuric acid carefully added. Spoiled meals will give 

 a characteristic, disagreeable odor, while fresh or unspoiled meals will give an 

 odor of paste or one resembling meat broth. 



2. Biological (Serological) Examination 



Biological methods of examination have now attained importance in the detection 

 of sources of adulteration and contamination of feeding stuffs. For the purposes 

 in question, precipitation and complement fixation are the chief biological methods 

 employed. Anaphylaxis has only a very limited application. 



The biological methods are specific albumen reactions. 



Biological reactions are resorted to, above all, in cases where the adulterants oi 

 undesirable admixtures are not sufficiently characteristic morphologically to be 

 definitely recognizable by botanico-microscopical means. Biological reactions have 

 become of considerable importance in the detection of castor oil seeds. While the 

 seed skins are easily recognized by their radial palisade cells (Fig. 84), the botanico- 

 microscopical determination of the toxic decorticated seeds, which have in late 

 years been used as adulterants of oil cake, is not sufficiently accurate. 



Complement fi.xation with specific serum is a definite means for the detection of 

 the poisonous castor oil beans. This reaction is strictly specific and will reveal the 

 presence of 0.5 percent of castor oil beans in a feeding stuff. The toxic principle 

 of the castor oil bean is destroyed by heating at 212° F. for five minutes. Seeds 

 thus treated fail to give the complement fixation reaction. 



With reference to technic of the complement fixation test, see Klimmer, Handbuch 

 der Nahrungsmitteluntersuchung, Vol. 3. Anti-ricin serum may be obtained from 

 Merck, Darmstadt, or may easily be produced by careful immunization of rabbits. 

 The first dose per 1 kg. live weight consists of 0.001 mg. ricin Merck, subcutaneously 

 injected, followed in 8 to 10 days with 3 to 5 or 8 to 10 times the first dose. In 

 regard to testing the serum, see Klimmer's work just referred to. 



According to Miessner, as well as according to Pfeiler and Engelhardt, the pre- 

 cipitation test is also of practical value. 5 percent adulterations, sometimes as low 

 as 1 per cent, may be detected with certainty. 



Whether the "rapid method" (Thermo-precipitation) recently recommended by 

 Kranich gives sufficiently accurate or reliable results is yet to be demonstrated. The 

 difficulties attending the use of the precipitation test in the detection of the source of 

 vegetable albumens lie in the fact that plant extracts (bean meal, rice, barley, field 

 beans, soy beans. Stramonium, castor oil beans, etc.) frequently produce precipitates 

 with normal sera. 



Agglutinins (conglutinins) for red corpuscles which are present in some plants 

 are of value only under certain specific conditions and when used with the great- 

 est care, for the differentiation of vegetable substances. They are not adapted for 

 general use because they occur in a great variety of toxic (Ricinus, Croton, Datura) 

 as well as harmless (beans, peas, lentils, vetches) plants. 



The hemolysins are more promising in this respect. They possess the property 

 of dissolving washed red blood corpuscles in isotonic sodium chlorid solution (0.85 

 to 1 percent) (see Klimmer, loc. cit., p. 136). They occur, it seems, in only a very 

 few species of plants. The best known vegetable hemolysin is saponin which, as 

 is well known, is the toxic principle of corn cockle (Agrostemma githago). Saponin 

 occurs also in Saponaria officinalis (soapwort) and in Delphinium (larkspur), both 

 poisonous. The fact that it also occurs in the seeds of Atriplex (notchweed) and 

 Sorghmn^ saccharatxmi is of little importance, since it is present in traces only. 

 Hemolysins have also been found in the seeds of the sand vetch or winter vetch and 

 in the common vetch (Vicia villosa and V. sativa). 



Hemolysins may be used for the detection of corn cockle seed in meal, flour, bran, 

 bread, etc. This is of special importance when the characteristic perisperm of the 

 corn cockle seed has been removed. Rusconi's method consists in the preparation 

 of a doughy mass from 5 grams of the meal or bran in question and 4 grams of 

 a 2 percent solution of neutral sodium citrate. This dough is then worked through 

 a fine-meshed linen cloth with the gradual addition of 16 c.c. of the same citrate 

 solution. The liquid thus obtained is filtered, and 3 c.c. of the clear filtrate is 

 treated with 1 c.c. of a suspension of red blood corpuscles (1 to 100), incubated for 



