370 ON SOME POINTS IN THE 



I employed first in endeavouring to apply the antiseptic principle should have 

 been so admirably adapted for detergent purposes. And it has grieved me 

 to learn that many surgeons have been led to substitute needlessly protracted 

 and complicated measures for means so simple and efficient.^ 



As an instance of trouble misapplied in this matter, may be mentioned 

 preliminary washing with soap and water. If carbolic acid is the disinfectant 

 used, such washing is not only wholly unnecessary, but is, I believe, positively 

 injurious ; as it must tend to check the penetration of the germicide into the 

 substance of the epidermis, by saturating it with water for which carbolic acid 

 has so little affinity. That this practice is superfluous is, I venture to think, 

 proved by my experience, as I never in any case adopted it. 



The incomparably greater attraction of carbolic acid for epidermis than 

 for water was strikingly illustrated by an experiment not hitherto published. 



[Here my letter was broken off, in consequence of other engagements. But I afterwards wrote 

 to Sir Hector Cameron what I had intended to say on this subject and he was good enough to incorporate 

 my remarks in his second lecture (see British Medical Journal, April 6, 1907, p. 799).] 



' The avidity with which carbolic acid seizes upon epidermic tissues was 

 strikingly illustrated by an experiment which he related in an unpublished 

 address to the medical students of Glasgow, delivered in 1894. 



' Having discovered a method by which the amount of carbolic acid present 

 in a watery solution could be determined,- he packed a test-tube closely with 

 hair of the human head, and added just enough five per cent, solution of carbolic 

 acid to cover it, eight times the weight of the hair being required for the purpose. 

 Half an hour later he poured out some of the liquid, and applied the test ; when it 

 was found that already nearly half the carbolic acid had been withdrawn by the 

 hair from the watery solution. 



* Considering that the hair was only an eighth part of the weight of the solu- 



^ The fear sometimes expressed of poisonous effects from carbolic acid, as used in antiseptic surgery, 

 is, so far as my experience goes, entirely groundless. 



* ' In the course of some work on the preparation of catgut for surgical purposes, he observed that 

 if a weak solution of chromic acid in water is mixed with carbolic lotion, the mixture, which is at first 

 a pale straw colour, gradually grows very much darker during the next few hours. This fact afforded 

 the means of estimating the quantity of carbolic acid in a watery solution. ^Making a mixture of 

 equal parts of the weak chromic liquid and a live per cent, watery solution of carbolic acid to serve 

 as a standard of comparison, and at the same time making a corresponding mixture of the chromic 

 liquid with the carbolic solution to be tested, and ascertaining how much the standard had to be diluted 

 in order to bring its tint down to equality with that of the mixture containing the liquid to be tested, 

 an estimate could be formed of the amount of carbolic acid present in the latter. Lord Lister informs 

 me that, on going over the subject again recently, he ascertained that hair retains this remarkable 

 power of withdrawing carbolic acid from a watery solution after all fatty matter has been removed 

 from it by prolonged steeping in sulphuric ether.' 



