1874.] Dr. W. Roberts on Biogenesis. 289 



Balfour Stewart, and Loewy. Recognizing the sun as the governor of 

 our system and the source of terrestrial heat and light, it appears certain 

 that at least some of the circumstances attending our globe are directly 

 or indirectly the results of solar conditions, of which we can read but too 

 few, and interpret still fewer rightly. In the present instance we see 

 that, as in other curves, a certain rainfall maximum may be less than 

 minima not immediately preceding or succeeding ; and this alone suggests 

 the desirability of comparison with actual magnitudes of sun-spot areas ; 

 but the introduction of this more accurate test would doubtless prove a 

 waste of time, unless the approximate relation at present under view can 

 be maintained. 



III. " Studies on Biogenesis." By WILLIAM ROBERTS, M.D., 

 Manchester. Communicated by HENRY E. ROSCOE, F.R.S. 

 Received March 3, 1874. 



(Abstract.) 



The object of the investigation is to inquire into the mode of origin of 

 Bacteria and toruloid vegetations. The inquiry is divided into three 

 sections. 



SECTION I. On the sterilization ~by heat of organic liquids and mixtures. 

 When beef-tea or a decoction of turnip is boiled for a few minutes and 

 afterwards preserved from extraneous contamination, it passes into a 

 state of " permanent sterility." 



This state is characterized by loss of power to originate organisms with 

 conservation of the power of nourishing and promoting the growth of 

 organisms. 



All organic liquids and mixtures seem capable of being brought to this 

 state by exposure to the heat of 212 F. ; but the length of time during 

 which exposure to this heat is necessary to induce sterilization varies 

 greatly according to the nature of the materials. Ordinary infusions 

 and decoctions were sterilized by boiling for five or ten minutes ; but 

 milk, chopped green vegetables in water, pieces of boiled egg in water, 

 and other mixtures were not sterilized unless the heat was continued for 

 twenty to forty minutes. Hay-infusion was sterilized, like other infu- 

 sions, by boiling for a few minutes ; but when the infusion was rendered 

 alkaline with ammonia or liquor potassse, it was not sterilized except 

 after an exposure to the heat of boiling water for more than an hour. 

 Sometimes it germinated after two hours, and once after three hours of 

 such exposure. 



There appeared to be two factors of equal importance in the induction 

 of sterilization namely, the degree of heat and the duration of its appli- 

 cation. These two factors appeared to be mutually compensatory in such 

 fashion that a longer exposure to a lower temperature was equivalent to 



