42 DISINFECTANT 



unlike this virus, it cannot multiply itsolf in tho animal economy to such an extent as 

 to endow within a fow hours every portion of its juices with tho power of producing 

 similar results. A virus, on tho contrary, renders the liquids of an infected animal 

 as virulent as the original germ. Strychnine may be regarded as the typo of a poison, 

 and vaccine matter as the typo of a virus. 



'Many considerations tend to show that the virus of cattle plague is a body siniil;ir 

 to vaccine lymph, and consists of germinal matter, or living cells, possessing physio- 

 logical individuality, which, if not exposed to extremes of heat, cold, or dryness, are 

 capable of preserving their activity for a certain time outside the living organism, of 

 adhering to material objects, and of being carried from one placo to another by cur- 

 rents of air ; each, when introduced into the blood, requires a certain time (known as 

 the period of incubation) during which tho septic germs developo and multiply, until 

 they have so far poisoned the blood that the ordinary symptoms of disease become 

 manifest. 



' The blood poisoning thus set up may legitimately be called "fermentation " ; it is a 

 decomposition caused by tho act of nutrition of the living cell, whereby it reproduces 

 in incalculable numbers tho specific septic germs which have given it birth. These 

 gradually infest the blood and other animal liquids, and as the disease progresses are 

 discharged from the skin, throat, glands, &c. ; the breath, perspiration, and excreta 

 of the animals forming vehicles for the distribution of the virus. By " living " cells, 

 is not meant living, in the sense in which an animal, or even a low form of infusoria, 

 lives ; but living as a seed, or as vaccine matter, even when dried, may be living, 

 inasmuch as it still possesses reproductive vitality. 



1 It is by no means certain that the multiplication of these individual cells is tho 

 immediate cause of the blood poisoning. The analogy of the action of virus on tho 

 blood, to that of yeast on sugar, renders it more probable that this is not the fact. 

 In the case of the best-known ferment yeast its cells multiply by feeding upon the 

 sugar in the liquid ; alcohol and carbonic acid being their excretions. It is therefore 

 probable that during the multiplication of the virus clls, they, in a similar manner, 

 impoverish and weaken the blood, by feeding upon some element in it, whilst at tho 

 same time they excrete a poison to which the symptoms of the disease may be imme- 

 diately due.' 



Passing over that portion of the report which deals with the usual disinfectants 

 which have been already dealt with by Dr. Angus Smith, the passages, which espe- 

 cially relate to the Tar acids are selected on account of the value of the experimental 

 evidence they give. 



' The Tar Adds (Carbolic and Cresylic Acids). These two bodies are so commonly 

 known under the name of acids, that I shall continue so to designate them, although 

 by chemists they are -more generally classed with the alcohols. They have groat 

 similarity, and only within the last few months have they been met with separately in 

 commerce, having hitherto been both called carbolic acid. Creosote, (ttpfas ffueiv, to 

 preserve flesh), prepared from coal-tar, one of the most powerful antiseptics known, 

 was thought to be impure carbolic acid, until 1854, when Professor Williamson and 

 Mr. Fairlie, in an investigation of it, discovered that it was a mixture of carbolic and 

 cresylic acids. It was then taken for granted that Reichenbach's creosote, from wood- 

 tar, had a similar composition, until Hlasiwetz, in 1858, showed that this creosote was 

 a different body from carbolic or cresylic acids. Finally, Dr. Hugo Miiller, in 1864, 

 discovered that true creosote, and its analogue guaiacol, belonged to a different class 

 of bodies, and consisted of methyl-oxy-phenic and methyl-oxy-cresylic acids. No ex- 

 periments on the large scale have yet boon tried with true creosote, as I have only 

 been aware within the last few weeks that this compound could bo obtained in 

 quantity. 



'Pure carbolic acid is a white crystalline solid, melting at 34 C., and distilling nt 

 180 C. ; a trace of water or oily impurity renders it liquid, and for disinfecting pur- 

 poses it is always supplied in this form, to avoid tho extra expense and trouble nei-drd 

 for the separation of tho last traces of impurity; cresylic acid is liquid, it boils at 

 203 C., and closely resembles carbolic acid in odour and other properties. r>"l'< TO 

 the commencement of these inquiries it was thought to bo of little or no value ns a 

 disinfectant, but Dr. Angus Smith has lately shown that it rivals, if it docs not sur- 

 pass, carbolic acid in antiseptic properties. For tho present purpose of cattln-j.lngun 

 disinfection it is immaterial which acid is used, and to avoid unnecessary repetition I 

 shall use the term " carbolic acid " to express either acid, or the commercial mixture of 

 the two acids. 



4 From time immemorial carbolic acid, creosote, or bodies containing them, have been 

 used as antiseptics. Passages in Pliny, read by tho light of chemical science, show 

 that the Egyptians used for embalming their mummies a compound made from pitch, 

 which must have contained large quantities of creosote. Carbolic acid is tho active 



