THE ANTITOXIN. 
Preparation . — The antitoxic serum was prepared at Parke, Davis & 
Co., Detroit, Mich., hy Passed Asst. Surg. John F. Anderson, Assist- 
ant Director of the Hygienic Laboratory. 
Two horses were selected which had furnished a reliable high potency 
serum. These horses had been treated in the usual manner hy grad- 
ually increasing doses of the diphtheria toxine. 
From horse Xo. 781 six liters of blood were drawn on June 11, 1901, 
at 9 a. m. The blood was drawn into 12 large test tubes, each 
tube containing approximately 500 c. c. Immediately after bleeding 
the blood was placed in a room, the temperature of Avhich was about 
25° C. 
The next day, June 15, at 8.30 a. m., the horse was again bled for 6 
liters, also into 12 tubes. This blood was placed with the lot drawn 
on the 11th. 
After the blood had been clotted several days the clear serum was 
poured from the 21 tubes into a special bottle. Only that serum which 
was perfects clear and entirely free from coloring matter was used. 
As the serum did not separate from this blood as clearly as usual, onh" 
1,378 c. c. of serum were obtained from the 21 tubes. The serum was 
at once examined for potency and found to contain approximately 500 
units. It was also tested bacteriologically for purity and no growths 
were obtained in bouillon tubes. After the samples were taken for 
testing, 20 c. c. of pure chloroform were put into the bottle with the 
serum, which was then at once placed in the ice chest at a tempera- 
ture of 1.7° C. Chloroform was added to the serum to prevent any 
possible contamination. All of it of course disappeared with the 
vacuum under the diwing process. 
On June 22 evaporation of the serum was accomplished by bubbling 
dry air through the serum with a moderate vacuum. The vacuum 
varied from 20 to 23 inches. The arrangement for diwing the serum 
is well shown in the accompanying illustration (fig. T). The serum 
was syphoned into the large drying tubo in small quantities, and the 
warm air bubbling through rapidly dried it and at the same time pre- 
vented the formation of hard cakes. The water bath surrounding the 
tube containing the serum was kept at about 35° C. ; it varied from 
32° to 36° C. throughout the operation. The temperature of the dry 
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