Collecting and Testing Bloods 63 



investigation. It appeal's also to take place in stored antisera at times. 

 It is not due to evaporation in stored dilutions, nor to the prolonged 

 action of the chloroform added for purposes of preservation, nor to 

 knctrrial development, for pure sterile sera preserved in sealed tubes 

 have repeatedly given greater reactions. This observation has not as 

 yet been recorded. Although it appears at first sight improbable that 

 a dried serum or blood may (as long as it remains soluble) give an 

 increased reaction after a time, the matter will have to be submitted to 

 experiment. 



In a few instances the sera were dried on glass plates at 37 C., the 

 scales being preserved in bottles with slightly vaselined stoppers. In 

 the majority of cases the bloods or sera were collected on strips of 

 filter-paper of fairly uniform size (3 by 5 inches), as noted in the paper 

 by Nuttall and Dinkelspiel (July 1901, p. 378) and in a circular letter 

 which I sent out to those who have kindly aided me in collecting bloods 

 in various parts of the world. The filter-paper is immersed in the 

 serum or defibrinated blood, clots being avoided, after which it is hung 

 up to dry. One end of the strip is left clean, so that the name of the 

 animal (both common and scientific), the date, place of collection or 

 natural habitat, and the name of the collector, can be noted thereon in 

 lead-pencil. The notes can be written clearly if the paper is rested on 

 a hard surface. The strips of paper dry rapidly when suspended in the 

 air, it being convenient to pin them against the edge of a table or shelf 

 or upon the branch of a tree. Collectors were particularly warned not 

 to allow strips of paper saturated with different bloods to come in 

 contact with one another, especially in a moist state. Where it was 

 impossible to wait for the strips to dry, as when out shooting, collectors 

 were requested to place each sample separately in the paraffined paper 

 covers which I supplied, these being of the pattern usually used by photo- 

 graphers. The outfit for collecting which I sent out consisted, then, 

 simply of pure filter-paper of fairly uniform thickness, accompanied by 

 paraffined envelopes and outer envelopes of ordinary stiff paper. On re- 

 turning from shooting, the moist strips were removed from the paraffined 

 covers and hung up to dry. The drying may be facilitated in our climate 

 by exposing the strips to the sun, but this proceeding does not appear 

 to do in the tropics, for I have found several samples sent from hot 

 countries to have become insoluble. The fact that blood-stains may 

 frequently become insoluble in hot countries was noted in a letter to me 

 from Mr E. H. Hankin, of Agra, India, dated 23 August, 1901. He wrote, 

 "There is a practical difficulty in carrying out the test here in the 



