40 NATURE AND OBJECTS OF PHYSIOLOGICAL SCIENCE. 



selves, by the want of the necessary conditions. When these conditions 

 are supplied, the state of vital activity is resumed, and all the functions 

 of life go on with energy. 



44. Of this Dormant Vitality it may be well to adduce some exam- 

 ples ; which may assist in impressing on the mind of the student the 

 general views here put forth. This condition is manifested in the most 

 remarkable manner by the seeds and germs of plants ; many of which 

 are adapted to remain, for an unlimited period, in a state of perfect 

 repose, and yet to vegetate with the greatest activity, as soon as ever 

 they meet with the necessary conditions. Thus the sporules of the 

 Fungi, which can only develope themselves in decaying organized mat- 

 ter, seem universally diffused through the atmosphere, and ready to 

 vegetate with the most extraordinary rapidity, whenever a fitting oppor- 

 tunity presents itself. This at least appears to be the only feasible 

 mode of explaining their appearance, in the forms of Mould, Mildew, 

 &c., on all moist decaying substances ; and that there is no improbabi- 

 lity in the supposition itself, is shown by the excessive multiplication of 

 these germs, a single individual producing not less than ten millions of 

 them, so minute as when collected to be scarcely visible to the naked 

 eye, rather resembling thin smoke, and so light as to be wafted by 

 every movement of the atmosphere ; so that, in fact, it is difficult to 

 imagine any place from which they can be excluded. Moreover, it is 

 certain that an equally tenacious vitality exists in the seeds of higher 

 plants. Those of most species inhabiting temperate climates are 

 adapted to remain dormant during the winter ; and may be easily pre- 

 served, in dry air, and at a moderate temperature, for many years. 

 Some of those which had been kept in the Herbarium of Tournefort 

 during upwards of a century, were found to have preserved their ferti- 

 lity. Cases are of no unfrequent occurrence, in which ground that has 

 been turned up, spontaneously produces plants dissimilar to any in 

 their neighbourhood. There is no doubt that in some of these cases, the 

 seed is conveyed by the wind, and becomes developed in spots which 

 afford congenial soil, as already remarked in the case of the Fungi. 

 Thus it is commonly observed that clover makes its appearance on soils 

 which have been rendered alkaline by lime, by strewed wood-ashes, or 

 by the burning of weeds. But there are many authentic facts, which 

 can only be explained upon the supposition, that the seeds of the newly- 

 appearing plants have lain for a long period imbedded in the soil, at 

 such a distance from the surface as to prevent the access of air and 

 moisture ; and that, retaining their vitality under these circumstances, 

 they have been excited to germination when at last exposed to the re- 

 quisite conditions. Thus Professor Lindley states as a fact, that he 

 has raised three raspberry-plants from seeds taken from the stomach of a 

 man, whose skeleton was found thirty feet below the surface of the 

 earth, at the bottom of a barrow which was opened near Dorchester ; as 

 his body had been buried with some coins of the Emperor Hadrian, 

 there could be no doubt that the seeds were 1600 or 1700 years old. 

 Again, there are undoubted instances of the germination of grains of 

 wheat, which were enclosed in the wrappers of Egyptian mummies, 



