22 VIEWS OP THE MICROSCOPIC WORLD. 



LIFE AND RESUSCITATION. Infusorial animalcules live but a short period, for, al- 

 though the duration of their life varies in different kinds, it extends only from a few 

 hours to several weeks. Wheel animalcules have been seen in the enjoyment of 

 their existence twenty-three days after their birth. The death of Infusoria is usu- 

 ally sudden, and in the larger species is attended with spasms. The soft parts rap- 

 idly decompose after death, and all the curious and elaborate organs of these singu- 

 lar beings entirely vanish ; nothing appearing to remain except the firm, enduring 

 shells in which many kinds of the Infusoria are encased. But, in numerous instances, 

 this death is but apparent; the decay of the body does not take place, and in the 

 minute speck that lies before us like an atom of inanimate dust the mysterious 

 principle of life is still in existence. The creature may remain motionless for 

 months, and even years; but when it is again subjected to influences favorable to 

 its resuscitation, it awakens from its torpor, and life, with all its former energies, 

 is once more fully displayed. 



This surprising phenomenon is supported by undoubted proof. "When the water 

 containing a wheel-animalcule evaporates, the creature apparently expires, becomes 

 dry and hard, and may be preserved in this state for years, if buried in sand. 

 When placed in water in this condition, it will revive in a few minutes, and soon 

 swim about with its wonted activity. In 1701 Leuwenhoeck observed this fact in 

 wheel animalcules, and revived some specimens after keeping them dry for twenty- 

 one months. Baker obtained the same result after a longer time, and Prof. Owen 

 was present at the resuscitation of an animalcule after it had lain dormant in dry 

 sand for four years. Nor is this all; for such is the tenacity of life in these minute 

 beings, that the same animalcule may repeatedly pass through these phases of ex- 

 istence before it really expires. Mantell remarks that some wheel animals were 

 alternately dried and rendered torpid, and then again revived twelve times, and at 

 each resuscitation were as active as at first. 



The eleventh revival was witnessed by Spallanzani ; and he leads us to infer 

 that, upon moistening a portion of sand containing wheel- animalcules for the 

 fifteeenth time, many of them once more awoke from their stupor ; but this was the 

 last effort of vitality, for upon being dried and moistened again, no resuscitation 

 occurred. The wonderful legend of the Seven Sleepers is here more than realized ; 

 and in the Infusorial world the romantic fiction of Rip Van Winkle becomes a 

 sober statement of fact. Thus it is that Fancy in her wildest flights seldom sweeps 

 beyond the circle of truth. 



It is the opinion of Dr. Ehrenberg, in regard to this subject, that if the animal- 

 cule is entirely dried up and its natural heat lost, life is extinguished, but if this is 

 not the case the creature will remain in a torpid and motionless state, capable of 

 being revived; its body wasting away to an extent equal to the amount of nour- 

 ishment necessary for the support of its life. 



INFLUENCE OF TEMPERATURE. Infusorial animalcules are capable of existing 

 throughout a great range of temperature, but eventually perish under extreme de- 

 grees of heat and cold. If water, filled with Poly gastric Infusioria, be gradually 

 raised to a temperature of 125 Fah., these creatures will live. If the increase of 

 temperature be sudden they die at 140 Fah., notwithstanding it be kept up only 

 for half a minute. The Rotatoria, when put in boiling water (212 Fah.), are killed, 

 but they retain their power of revival when the water has a temperature varying 



