AGGLUTININS AND PRECIPITINS 103 



reaction follow this type of transfusion. We cannot enter here into 

 a discussion of methods of transfusion. 



Methods for Testing Human Blood. The simplest method depends upon 

 the preservation in the laboratory of known Group II and Group III sera. These 

 should be selected so that they have a relatively high titer, and should not be 

 employed if they titrate less than i to 16. The method to be described is essen- 

 tially that of Lee and Minot. The apparatus includes a few 7x75 mm. test-tubes, 

 a platinum loop, microscope slides with at least one built up on the ends with 

 pieces of glass rod or match sticks glued on by means of balsam so that another 

 slide may be inverted upon it with hanging drops. A microscope is useful but 

 not essential, since a hand lens of 10 diameters magnification is satisfactory. A 

 small moist chamber is desirable but not essential. In well equipped labora- 

 tories the serum may be kept in the ice chest in sterile ampoules or small bottles 

 and drops removed as required. Somewhat more satisfactory is preservation 

 in sections of drawn out glass tube similar to that used for vaccine virus. Each 

 small tube contains serum for one test and the serum may be blown out exactly 

 as is done with vaccine virus. Phenol 0.5 per cent, may be used as a pre- 

 servative. One-half cubic centimeter of physiological salt solution is placed in a 

 test-tube, and to this are added one or two drops of blood, obtained by ear or 

 ringer puncture, sufficient to make a slightly opaque emulsion. Clotting of the 

 mixture is not harmful since subsequent shaking of the tube will produce a 

 homogeneous suspension. Upon a microscope slide are placed one drop eacli of 

 the sera of Groups II and III. With the platinum loop a drop of blood suspension 

 is mixed, by gentle rubbing, in each of the serum drops and the slide immedi- 

 ately inverted upon the prepared slide or a small rack so as to make hanging 

 drops. At the end of five or ten minutes the reaction occurs and may be seen 

 with the naked eye ; in order to avoid mistakes owing to slight agglutination it 

 is important to observe with the 16 mm. lens of the microscope or a hand 

 lens. If a small number of specimens is examined it is well to have controls 

 with known I, II or III cells. If the reaction is delayed the slide should be kept 

 in a moist chamber for one-half hour and then observed. The group to which 

 the cells belong is determined by the following section from the chart of 

 inter-agglutination : 



STANDARD SERA 



II. III. 



2 I. _ 



3 n - - + 



CJ III. + - 



IV. + + 



Thus if the cells are agglutinated by both sera they belong to Group IV; if 

 not agglutinated at all and the control cells show that the sera agglutinate prop- 

 erly the cells belong to Group I; if agglutinated by only III serum they belong to 

 Group II, and if agglutinated by only II serum they belong to Group III. 



Hanging drops are not essential, but serve to make the reaction somewhat 

 clearer. The reaction occurs with the slides upright. In this case cover slips 

 may be used. Many employ undiluted blood and cover with cover slips, but 

 rouleaux formation sometimes offers a confusing picture. 



It has been suggested that since the important point of determination is as 

 to whether or not the donor's corpuscles are agglutinated by the patient's serum, 

 the latter may be separated and placed on a slide with the donor's corpuscles. 

 The separation of the serum requires more time than a complete test as given 

 above, and is subject to serious error if the patient's serum happens to be of low 

 agglutinin titer. 



If standard sera are not available they may be prepared if a known II or 

 III blood can be obtained. The interaction of the cells and serum with fifteen or 

 twenty other bloods can be worked out on the basis of the chart on inter- 

 agglutination. Space does not permit of giving the details, but Brem's method 

 gives them accurately. If this cannot be done the method of Rous and Turner 

 is probably the best of the methods for use where standard sera are not to be 

 had, since this method determines the activity of both the cells and serum of 

 the donor and recipient. The method with slight omissions is taken directly 

 from the article of Rous and Turner in volume 64 of the Journal of the Amer- 

 ican Medical Association. 



