Volume 1

Second interim report of the Royal Commission appointed to inquire into the relations of human and animal tuberculosis. Part II. Appendix.

  • Great Britain. Royal Commission on Tuberculosis (Human and Animal)
Date:
1904-1913
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Second interim report of the Royal Commission appointed to inquire into the relations of human and animal tuberculosis. Part II. Appendix. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

    14/778 (page 8)
    •give the numbers just as they work out, and to leave it to others to lop off whatever they may regard as the negligible quantity. My own opinion is that these numerical estimates have proved of distinct value to my colleagues in the calcula- tion of their doses. But the method, though useful, has its limits ; and these limits have, I think, occasionally l:)een overstepped. For example, in one of my estimates I calculated the number of bacilli per c.c. to be 78,-506,666. Everybody will understand that the margin of possible error in this enormous figure must be, at least, some few millions. It is obvious that an estimate of an emulsion so rich in bacilli as this can only be regarded as useful for the calculation of l:>ig doses. It is not an estimate which justifies the calculation of a dose of 1.3,000 bacilli by mere dilution of the original material; but this, I see is the alleged dose of this emulsion with which a bovine was inoculated. Comparison with Culture Doses. My colleagues use for culture inoculations bacilli grown on serum. These are finely emulsified, with the aid of saline solution, and their bulk after centrifugalisation is measured. One cubic millimetre is taken as equivalent to one milligramme. It is therefore of interest, in order to compare tissue emulsion doses with culture doses, to consider the prob- able numlDer of bacilli contained in 1 cubic millimetre of bacilli grown on serum. Bacilli grown on serum, even when so finely emulsified that they are suitable for intravenous inoculation into rabbits, form innumerable clumps in which the bacilli are so tightly glued together that it is impossible to count them. After considering possible ways of overcoming this difficulty, I have formed the opinion that reliable estimates of serum-grown bacilli cannot be made by actual counting, on the lines of my tissue emulsion estimations. There is, however, no difficulty about forming a rough calculation of the number of serum-grown bacilli con- tained in a given volume of culture. The length of the serum bacillus varies from about '75 fi to about 2*5 ^ and generally averages about 1 fi. The breadth is about 35 /J. on the average. We may then, by elementary arithmetic, calculate how many bacilli, measuring 1 m by '.35 M and closely packed together, would occupy a cubic millimetre. The number amounts, roughly, to 8,000 million. This number is no doubt higher than the num- ber actually contained in 1 c.mm. of centrifugalised bacilli, Ijecause the bacilli cannot be regarded as all being in close contact with each other. Making allowance for this consideration, probably from 4,000 to 5,000 millions is a rough approximation to the actual figure. This calculation, admittedly very imperfect, is at least sufficient to show that the great majority of culture inoculations which have been made are very much richer in bacilli than the inoculations with even the largest doses of tissue emulsions. Arthur Eastwood.