On Spontaneous Generation. 373 



Pediculi ; there are also the Pediculi corporis et pubis hu- 

 mani, &c. The following plants or growths, as the hair of 

 the head, and other parts of the body. The teeth and hollow 

 bones may be compared with lithophytes. To the anoma- 

 lous or incidental productions belong the Acarus scabiei and 

 scab, senilis, the one which forms the most striking symptom 

 of the disease called phthiriasis, intestinal worms, the ani- 

 malcules which have been observed in many morbid secre- 

 tions ; as for plants or growth, different eruptions of the skin, 

 which complete a regular circle of dev elopement, and have a 

 stage of fructification, which proves either capable of propa- 

 gating the species, (the pustules of the small pox, &c), or 

 abortive, (boils, &c); moreover growths that are less denned 

 in their developement, as the polypous and fungous excres- 

 cences ; lastly, minerals, as the calculi found in different or- 

 gans, the anomalous ossifications of arteries, &c. Most of 

 the animals thus spontaneously generated, afterwards propa- 

 gate their species by ova, and some of the growths by seeds 

 or sporules, by which they may be transmitted to any 

 other human organism that may be favourably predisposed 

 for their reception. Here therefore we observe a little world 

 of natural productions, the possibility of whose spontaneous 

 generation is offered by any human body called into existence. 

 The analogy between what we observe in man, and what 

 must have happened, and still occasionally happens, on an 

 extensive scale, on the surface of the globe, which no philo- 

 sopher of the present day would consider as a dead and ran- 

 dom aggregate of matter, is, I think, quite striking. The earth 

 since the general incandescence of its surface, has had a num- 

 ber of stages of developement, the latest of which are marked 

 by the organic creations of the transition, secondary, tertiary, 

 and the present series. Each of these stages or epochs had, 

 probably, a period when the creative power was most active, 

 and which gave rise to the great majority of the organic be- 

 ings of each series, by spontaneous generation. But acciden- 

 tal or incidental circumstances, to which, in the present epoch 

 belong the changes which the free operations of man effect 

 on the surface of the globe, have, I think, at a much later pe- 

 riod given rise to the partial and local generatio spontanea of 

 organisms, either coinciding with some already existing, or 

 presenting a specialization of their own. Where, for exam- 

 ple, the stratified rocks of any epoch were first pierced by a 

 volcanic eruption, the decomposition of the plutonic rocks, 

 thus brought to the surface, probably gave rise to the exist- 

 ence of new organic beings. How could we otherwise ac- 

 count for the peculiarities of the floras of volcanic districts, in 



