70 The Precipitins: Methods 



produced, is incidentally given in connection with the tests on the bloods 

 of Pisces. It will be seen that no general picture, other than a sub- 

 jective one, could be gained of the results until the conclusion of the 

 work, when the tables had been completely rearranged, the bloods being 

 placed in their zoological order and the antisera in theirs. 



On receipt, the samples on filter-paper were cut in two after 

 numbering, the one half being placed in order according to system, the 

 other half in order according to number. The systematic collection 

 aided materially in the final arrangement of the tables, and permitted 

 of small series of tests being made upon isolated groups, the bloods 

 being readily found. In both collections the samples were pinned upon 

 clean sheets of paper which prevented their coming in contact with one 

 another. The slips of the collection by numbers were ordered in groups 

 of 20 in paraffined envelopes enclosed within envelopes of stiff paper. 

 All the samples on filter-paper were kept at room temperature. 



When a new antiserum had been produced I began by testing 

 down from blood No. 1 to the end of the list. 



The test-tubes containing the blood solutions were numbered and 

 ordered in a manner corresponding to the numbers on the racks. The 

 solutions were drawn up by means of the pipette (Fig. 3 A, p. 65) and 

 transferred to tube 1 of racks A, E, I, M (for a series of 80), then the 

 second blood dilution was allowed to flow into tube 2 of the same 

 racks, and so on to the end of the series. This system rendered any 

 confusion practically impossible. 



When the tubes had all been filled, the racks were transferred to 

 a stand (Fig. 4) which I constructed at small cost and have found 

 essential in the work. The stand consists of narrow shelves of deal 

 attached to wooden uprights by means of galvanized brackets. Metal 

 T-pieces are attached to both ends of the uprights, the one in each case 

 serving for the attachment of a strip of wood which serves as a base, 

 the other for the attachment (at one extremity of the T), of a brass 

 wire cord which runs down vertically to its attachment, a screw eyelet, 

 screwed into the basal strip of wood. A piece of dull black silk riband 

 sewed to two strips of bent zinc at both ends slides up and down 

 along the wires, wear being prevented by the zinc, within the bend 

 of which the wires run. Small tacks are placed on the posterior upper 

 margin of the shelves to prevent the racks being pushed backward 

 off the shelf. The whole stand, and the racks, are painted black. 

 Each stand carries two racks side by side. Where a series of 80 bloods 

 is being tested, it is necessary to place two stands side by side to 

 accommodate the racks in their proper order. 



