The examination of cow's milk for the detection of pathogenic properties / by Sheridan Delépine.

  • Delépine, Sheridan, 1855-1921.
Date:
[between 1890 and 1899]
Catalogue details

Licence: Public Domain Mark

Credit: The examination of cow's milk for the detection of pathogenic properties / by Sheridan Delépine. Source: Wellcome Collection.

Provider: This material has been provided by The University of Glasgow Library. The original may be consulted at The University of Glasgow Library.

    5/32 (page 5)
    as possible, I have thought it also desirable in each case to apply a few tests showing the state in which the specimen was when I received it and, roughly, the quality of the milk. For this purpose I have, whenever possible, taken the reaction, the specific gravity, the amount of cream that could be separated in a quarter of an hour by means of the centrifugal machine (giving 3000 revolutions to the minute), the amount of sediment, the number of cells, and the total amount of bacteria present. In all cases the specimens were examined the same day as I received them. 3. Even if tubercle bacilli were equally distributed through tuber- culous milk (which they are not), a very large number of them would have to be present before one could expect to find one bacillus now and again in the few drops of milk used for microscopical examination. To examine completely I ounce of milk microscopically it would be necessary to make at least 500 microscopical examinations, for not more than one drop can be examined at a time. If there were about 100 bacilli in that ounce of milk it would be necessary to examine on an average five drops of it before one bacillus was dis- covered. To prepare and examine each drop thoroughly does not take less than twenty or thirty minutes, so that the practicability of microscopical examination is much diminished by the length of time it requires and the considerable labour it involves when bacilli are very few. Yet one bacillus in each five drops would correspond to a total of about 5000 bacilli in a single glass of milk, or 10,000 in a pint 1 When the milk of a cow suffering from well-marked tuberculous udder, is examined unmixed with other milk it is often found that it contains small curdy masses in which many bacilli may be discovered, so that examining more specially these small masses it becomes possible to discover the bacilli within a reasonable time. In the case of mixed milk such as is obtained in our town dairies it is necessary to have recourse to some other device to obtain the bacilli in sufficient numbers for demonstration. The simplest way is to cause the impurities contained in some ounces of milk to separate as a sediment, and then to examine a part of that sediment. As it is desirable not to allow the milk to stand exposed to various contaminations for any length of time, it is advis- able, in order to obtain the sediment rapidly, to make use of the centrifugal machine. The sediment obtained from 80 ccm. of milk {i.e. a little less than 3 ounces) is far too bulky to be examined entirely with the microscope. In most cases I have been able to examine only a small fraction of such a sediment. From this it will be evident that whenever tubercle bacilli are discovered by the microscopical method they must be in such abundance as to make the milk infectious in a very high decree. I may say at once that out of some forty specimens o{ uninixed^iuil 'k obtained at various times from tuberculous cows I have found the bacilli abundant in microscopical preparations only in two cases and m these cases the udder was much diseased, in two other cases tubercle bacilli were found in small numbers, and that, only after a very careful search. By the inoculation method 20 to 25 per cent of