INFECTION AND DISINFECTION. 769 



nected with putrid decomposition were regarded as a sufficient cause 

 for the development of fever, small-pox, etc. It can not be denied 

 that gaseous matters, notably sulphureted hydrogen, may act as poi- 

 sons and cause many serious symptoms, but it has never been shown 

 that infectious diseases originate in this manner. It is contrary to all 

 that chemistry teaches us, that sulphureted hydrogen or ammoniacal 

 vapors inhaled by the lungs should increase within the body and cause 

 it to become a center of infection ; and we know likewise that ordinary 

 poisons — e. g., arsenic or morphia — fatal as their effects may be to one 

 individual, have no power of increase and propagation after being once 

 taken. It is therefore evident that the poisons of infectious diseases 

 must be something of an entirely different nature. "We know that 

 they multiply in the system to an almost infinite extent, and that every 

 one of the myriads of atoms thus developed is as potent for evil as the 

 atom from which it originated. The possession of this and other prop- 

 erties clearly indicates that the contagious agencies are independent 

 living organisms, capable of growth and reproduction. It has long 

 been known that certain diseases of the skin — e. g., ringworm — are 

 caused by the presence of parasites, which very rapidly increase, and 

 can be easily recognized under the microscope. 



In the case of some three or four of the infectious diseases it would 

 seem that the poison has really been discovered. On examining vac- 

 cine matter, the contents of the pocks in small-pox, and discharges in 

 glanders, the microscope shows a vast number of infinitely minute 

 particles, which appear as glistening points. Some of these are even 

 less than the fifty-thousandth of an inch in diameter, and it therefore 

 follows that very high powers are necessary for their detection. Such 

 particles, obtained from vaccine lymph, have been washed in water ; 

 the water when inoculated did not produce any effect, but the washed 

 particles were found to have retained their potency. It seems fair to 

 infer that the contagious agents of the other infective diseases would 

 resemble in their physical characters that of vaccine, and the nature of 

 such particles is the important problem that offers itself for solution. 

 They are supposed by some, and notably by Dr. Beale, to be of an 

 animal origin, and to consist of elementary living matter, termed bio- 

 2)lasm. Such particles may be easily transferred from an infected to 

 an uninfected organism, in which they will manifest their own specific 

 powers, and grow and multiply almost indefinitely, exciting in their 

 new home a series of changes resembling those which characterized 

 their presence in the one from which they were derived. This account 

 is certainly correct as regards the virus of vaccine, but it does not 

 precisely define the nature of the particles or tell us anything of their 

 origin. Dr. Beale, however, states that particles of contagious bio- 

 plasm are not generated in the organism of the infected animal, but 

 are introduced from without, and were originally derived by direct 

 descent from the bioplasm of the body of man or animal. lie regards 

 vol. xxx. — 49 



