1877.] 



the Germinal Particles of Bacteria. 



421 



that we are not in a position to form any conclusion as to their size,, 

 excepting that they are so small as to be beyond the reach of observation. 

 Dr. Tyndall has taught us, first, that the optical effects observed when a 

 beam of light passes through a particulate atmosphere are such as could 

 only be produced by light-scattering particles of extreme minuteness ; 

 and, secondly, that by subsidence these particles disappear, and that the 

 contaminating property of the atmosphere disappears with them. He 

 has thus approximately determined for us the upper limit of magnitude, 

 but leaves us uncertain as to the lower ; for we have no evidence that 

 the particles which reader the atmosphere opalescent to the beam of the 

 electric lamp may not be many times larger than those which render it 

 germinative. Consequently the fact that the air may be rendered sterile 

 by subsidence, while affording the most conclusive proof that germinal 

 matter is not gaseous, leaves us without information as to the size of the 

 particles of which it consists. 



Of each germinal particle, whether inhabiting an aqueous liquid or 

 suspended in the atmosphere, it can be asserted that under conditions 

 which occur so frequently that they may be spoken of as general (viz. 

 moisture, a suitable temperature, and the presence of dead proteid matter, 

 otherwise called organic impurity) it produces an organism. If, for the 

 sake of clearness, we call the particle a and the organism to which it 

 gives rise A, then what is known about the matter amounts to no more 

 than this, that the existence of A was preceded by the existence of a. 

 With respect to A, we know, by direct observation, that it is an organic 

 structure ; but inasmuch as we know absolutely nothing as to the size 

 and form of a, we cannot even state that it is transformed into A, much 

 less can we say any thing as to the process of transformation. 



Considering that it is admitted on all hands that there exist in 

 ordinary air particles which are potentially germs, it might at first sight 

 appear needless to inquire whether or not this fact is to be regarded as 

 carrying with it the admission that they must necessarily possess the 

 other attributes of organized structure. Yery little consideration, 

 however, is requisite in order to become convinced that this question 

 stands in relation with another of fundamental importance in biology — 

 that, namely, of the molecular structure of living material *. It is 

 not necessary for my present purpose to do more than to indicate the 

 nature of this relation. As regards every form of living matter, it may be 

 stated that quite irrespectively of its morphological characteristics, which, 

 as we have seen, must be learnt by the application of the various methods of 

 visual observation at our disposal, it possesses molecular structure peculiar 

 to itself. We are certain of this because the chemical processes of which 

 life is made up are peculiar, that is, such as occur only in connexion with 



* The reader who is interested in this subject will find it discussed with great in- 

 genuity by Prof. Pfliiger, in his paper " Ueber die physiologische Verbrennung in den 

 lebendigen Organisinen," Pfluger's Archiv, vol. x. p. 300. 



