96 MEDICAL JURISPRUDENCE the serum of other species) Many workers prefer both intravenous and intraperitoneal injections of rabbits but the Imperial Serologist with the Government of India, who examines about 14,000 articles during a year and has perhaps the largest experience of this kind of work, prefers intravenous injections of blood serum in fowls except for antiavian serum for which he employs rabbits. He injects into the wing vein of a fowl 4 cc. on the first day, 8 cc. on the fourth day and kills the fowl on the twelfth day.jn order to collect the antiserum. w^ The following general remarks on the precipitin sera are quoted from the annual report of the Imperial Serologist for 1937-38 : — "(i) Some antisera produced against known sera are sometimes found unsuitable for the test. They do not yield sharp reactions in the required dilution and time, that is, they are not sensitive and are, therefore dis- carded. It may be noted that every individual fowl does not yield a 'suit- able serum ; some fowls may be entirely refractory and others may produce only weak sera. (ii) All antisera should be highly sensitive, reacting with solutions of animal sera in 1 in 1,000 dilution and reacting with a solution of human serum in 1 in 40,000 dilution. (iii) Some antisera react with sera which have not been used for their production, that is, they are not specific and should, therefore, be discarded In order to prove their specificity the worker must observe carefully that they do not react with 1 in 1,000 dilution of sera not used in their production. (iv) The antisera which give the expected result with a certain dilu- tion of a known serum (positive control) and do not give unexpected results with a certain dilution of known sera (negative controls) are only used." Application of the Precipitin Test.— The antisera which differentiate the blood of closely allied species of animals, e.g. cow's blood from buffalo's or sheep's blood from goat's are not prepared in the laboratory of the Imperial Serologist in Calcutta. But the blood of cow and buffalo (taken together) is differentiated from that of sheep and goat (taken together). This is carried out by means of two antisera, anti-buffalo and anti-sheep. The extract from a stain from any of these four animals will react with both the antisera but much more quickly with the antiserum corresponding to its group. The results so obtained is confirmed by testing further dilutions of the extract. A dilution will be found which will react with one of the two antisera only.22 , A? tjie pecipitin test indicates the presence of the blood protein of an aSmi ^ a known species its utility has been extended to protein materials other than blood stains The origin of skin, flesh, bone or even secretions such as saliva, milk and semen, is established by this test. Small fragments ot bones and remnants of soft tissues which are scattered deliberately to conceal ^ cases of murder are sometimes recovered by the police and sent lor their identification as also for the determination of their source A historical examination will indicate their nature and a serological exami- nation will reveal their source provided the fragments of the bones and soft tissues are not absolutely dry and decomposed. flp em?loyped f detecting the fraudulent substitution of flesh of horse cat dog, etc for beef, mutton and pork, and has been lately tnof wfl - tion ot norse tiesh, tor instance, in a sausage. Technique of the Test.-The first essential thing is to determine the presence of blood m a stain before proceeding with the serologicaTtest for 22. The Imperial Serologists3 Ann. Rep., 1937-38.