516 STATE BOARD OF AGRICULTURE. 



in its application and interpretation. To the last theme, we shall give the 

 weight of our attention. 



Inasmuch as we are intending to place the complete records of the 

 work with tuberculosis before our readers, it is expedient that we publish 

 the complete records of the tuberculin test of the college herd. In so 

 doing the test history of every animal will be constantly at hand for con- 

 sultation, if we should have occasion hereafter to refer to it, and should, 

 as we may expect, any of the animals not condemned at the present 

 time react in the future. These records will be complete to the present 

 time; and if anything of interest occurs in connection with the tests later, 

 we shall publish it in due season. 



We therefore have a two-fold object in view: First, to discuss the 

 application and interpretation of the test; second, to place on record the 

 tests as applied to the college herd. 



It is pertinent at the start that no one sufficiently interested in the 

 tuberculin test to study it for practical application should be satisfied 

 with the perusal of a single experience. A comparative and close study 

 is essential even after abundant personal experience may be brought to his 

 aid. 



WHAT IS TUBERCULIN ? 



Tuberculin was discovered by Koch in 1890 and considered by him as a 

 specific cure for tuberculosis. [Its value as a cure may be discussed in a 

 later bulletin. — Author.] 



Several months passed before he made known to the scientific world 

 its preparation. This was done through the Deutsche Medicinische 

 Wochenschrift in October of 1891. A meat infusion to which was added 

 four to six per cent, of glycerine and one per cent, of dry pepton was 

 placed in wide bottom flasks. These had been previously plugged with 

 cotton wool and sterilized. The flasks with their contents were then 

 sterilized in steam. They were now ready for inoculation with tubercle 

 bacilli taken from a pure culture. Some of the germs were floated on 

 the surf ace of this food material ; if the germs dropped to the bottom of the 

 flask there would be little growth. After an interval of about six weeks 

 there had formed a decided yellowish white scum over the surface of the 

 infusion which began to break up into small patches and fall to the bot- 

 tom. At this time it was concentrated to one-tenth its bulk and passed 

 through an unglazed porcelain filter to remove the germ sediment. This 

 gave a clear solution of tuberculin containing forty to sixty per cent, of 

 glycerine. The tuberculin is in solution and in this form is used. It can 

 be precipitated with alcohol; that is, upon the addition of alcohol a white 

 precipitate is thrown down which contains within it the active property 

 of tuberculin, but it cannot be regarded as pure tuberculin because of 

 the associated material which may also be precipitated with alcohol. 



The action of tuberculin is very peculiar; it is not strange that 

 Koch and his followers were led astray in regard to its curative prop- 

 erties. They noticed in their first use of it that when a very small amount 

 even less than one milligram was hypodermically injected a marked rise 

 of temperature would follow in tuberculous subjects, while sound sub- 

 jects would show no febrile reaction at all. Also, immediately about the 

 tuberculous lesion, if it were on the surface of the body and could be 

 watched, there would be a marked inflammation and many times slough- 



