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XII. Studies on Biogenesis. By William Roberts, M.B., Manchester. 
Communicated by Henry E. Roscoe, F.B.S. 
Received March 3, — Read April 16, 1874. 
Introduction. 
The question of the origin of Bacteria and Torulce lies so deeply at the root of some 
of the most important problems, not only of biology, but of pathology and practical 
therapeutics, that I make no apology for bringing forward the fruits of another investi- 
gation on the subject. 
The main question in controversy is whether these organisms originate de novo in the 
media where they grow, or whether they spring, like higher beings, from germs or 
parents like themselves. 
On the one hand it is contended that there exist in ordinary air and water (in addition 
to their proper elements) multitudes of germinal particles, and that the quasi-sponta- 
neous production of Bacteria and Torulce in organic media is in reality due to infection 
by these particles. On the other hand the existence of these supposed germs is 
doubted or denied ; and it is affirmed that these organisms can and do arise where 
infection by preexisting germs is impossible. 
It is important to bear in mind at the outset that these two theories (Panspermism 
and Abiogenesis) are not necessarily wholly destructive of each other. It is con- 
ceivable that, while the ordinary and common origin of Bacteria and Torulce is by 
procession from preexisting germs, there may also be conditions in which they arise de 
novo. At any rate it appears very desirable to establish the fundamental propositions 
of the panspermic theory, as broadly expressed in the preceding paragraph, on inde- 
pendent grounds, and without prejudice to the question of abiogenesis. 
The point of view here indicated is adhered to throughout this paper. It resembles 
the attitude assumed by pathologists in regard to contagious diseases. No pathologist 
doubts, for example, the contagiousness of small-pox, nor that the ordinary production 
and spread of the disease is due to infection. And this belief is not inconsistent with 
the notion, very commonly held, that in some previous age small-pox did arise de novo ; 
nor would it now be shaken, nor the practical deductions therefrom set aside, if it 
were proved that under certain rare etiological combinations small-pox might still 
arise de novo. 
The inquiry is divided into three sections. The first section is devoted to the 
examination of the conditions under which organic liquids and mixtures are rendered 
barren by heat. In the second section is investigated the question whether the normal 
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