MANUFACTURE OF HOG-CHOLERA SERUM 347 



paragraph, is now made ready for use. It is poured into a large 

 bottle which is graduated along one side, to show the amount of 

 virus it contains and the amount that is being injected. This 

 bottle is provided with a cork containing two holes, in each of which 

 is inserted a glass tube. One of these glass tubes merely passes 

 through the cork and opens into the top part of the bottle. To this 

 tube a small hand-pump is attached, by means of which air can be 

 forced into the bottle* This air raises the atmospheric pressure 

 in the bottle and forces the blood out through the other glass tube, 

 which reaches to the bottom of the bottle. Attached to the 

 upper end of this long glass tube is a rubber tube, 2 or 3 feet in 

 length, and on the end of this a needle intended for introduction 

 into the vein. This needle is hollow, and allows of the passage of 

 the virus blood from the rubber tubing into the vein of the animal. 

 Needless to s&y, this bottle, the glass tubes, rubber hose, and needle 

 are all carefully cleaned and rendered free from germs by boihng 

 before use. 



Many different types of needle have been devised for use in 

 this intravenous work. Some are simple straight needles, others 

 have a curved point, others have a peculiar curve to enable the 

 operator to get a more firm hold on them, and more carefully guide 

 their introduction into the vein, while still others are specially 

 ground, to prevent penetration through both walls of the vein. 

 Almost every man has some special preference for some particular 

 type of needle. A needle that is convenient for one man may prove 

 very awkward for another. The best plan is to try the various 

 types until you get one that seems to particularly suit your needs, 

 and then stick to it, or have the manufacturer make any change in 

 it that appears to be especially desirable from your standpoint. 



Estimating Dose of Virus. — Estimation of the dose of the virus 

 blood to be given is a very simple matter. It is merely a question 

 of the practice of the individual manufacturer. With a good virus 

 of high potency an injection of 5 c.c. of virus blood for each pound 

 weight of the animal is usually sufficient. This is the dose used at 

 the Ames serum plant and a number of the state plants. Some 

 men advocate giving as high as 7 c.c. of virus per pound, but, with 

 a good virus, this large dose is unnecessary. One of the advantages 

 •of the intravenous method is the fact that it requires less virus by 



