lo Sepi., 191^-] Hoic to make a Blood Si>nar. 555 



HOW TO MAKE A BLOOD SMEAR. 



By IF. A. N. Robertson. B.V.Sc. 



Numerous inquiries are made annually to the Stock Department for 

 information as to the probable cause of deaths amongst stock which occur 

 throughout the State. Occ-iisionally, in addhion to describing the .symp- 

 toms of sickness, si)ecimens of parts of organs, blood, &c., are forwarded, 

 in the hope that some information can be obtained. Such specimens, how- 

 ever, are almost useless, as changes, due to putrefaction, commence during 

 transit, and the organism responsible for this change either masks or destroys 

 any organism which may have been present as the cause of mortality. Useful 

 information, however, can be obtained from an examination of blood and 

 tissues if correctly taken ; consequently the accompanying description of 

 " How to make a Blood Smear" will prove useful if kept for reference. 

 The description is given of how to make a smear on microscopic slides ; these 

 are, of course, not always obtainable by the farmer, Vnit any slip of flat 

 glass will answer the purpose equallv well, and the smear may be made 

 with the end of a clean, unburnt wooden match. The essentials to be 

 borne in mind in following the method described are cleanliness and atten- 

 tion to detail, especially in regard to the drying of the smear in the air. 

 Glass upon which is a wet smear should never be put against another slip ; 

 each slip must be dried separately and wrapped in a piece of paper by 

 itself before forwarding. In addition, a very careful description of the 

 symptoms of sickness should be recorded, and on fost-mortcm examination 

 a minute description of the appearance of all the organs given. No detail 

 is too small to record if an accurate diagnosis is to be made. 



To Make a Blood Smear. 



{a) From tlie Living Aiiiinal . 



Blood may be taken from one of the \"eins which run along the upper 

 surface of the ear. The animal's head should be firmlv secured, and the 

 ear washed in solution of washing soda. A prominent vein should then 

 be pricked with a needle (an ordinarv clean sewing needle will do) or 

 with the point of a clean, sharp knife, or a fine inci-sion can be made on 

 the margin of the ear. As soon as the blood flows the smears should be 

 made; if delav occurs in spreading the film the blood will coagulate and 

 the .smear be a failure. Do not squeeze the vein in order to make the 

 blood flow ; it shfiuld occur quite naturally. 



{h) From the Dead Au'imal . 



Having opened the carcass, blood should be taken from the spleen or 

 lymphatic glands, and in the forwarding letter it should be stated from 

 which organ the smear was made. Cut the organ with a clean knife, and 

 scrape a small piece of the cut surface off with the edge of the glass slide. 



The first thing to be done is to prepare the glass slides on which the 

 blood is to be spread. The glass should be thoroughly cleaned, kept free 

 from dust, and should be polished with a cloth or handkerchief imme- 

 diately before use. 



To make the film, a very small drop of blo'-d. about the size of a 

 millet seed, should be put on one end of the_siide by means of either 

 the end of a wooden match or by the point of a knife, or by the needle 

 used for pricking the ear, or bv one of the corners of another glass slide. 



