30 GENERAL HISTOLOGY. 



forms the cuticle and its appendages, and, by folding over the 

 primitive streak, as it is termed, forms also the epithelium of 

 the canal of the spinal cord and of the ventricles of the brain. 

 Some histologists think that it forms the substance of the brain 

 and cord. The middle layer, or mesoblast, forms nervous, 

 muscular, connective, and vascular tissues, and the hypoblast 

 the epithelium of the internal organs. Fig. 5, PI. 2. 

 Further details are reserved for future study. 



6. DORMANT LIFE. 



Life may exist potentially without activity. The material 

 changes we have referred to are not essential to the existence 

 of the power on which life depends, since its activity, or func- 

 tions, may be suspended. This clearly indicates that the cause 

 of life differs from the material organization. The lack of 

 stimuli, or some unknown peculiarity, causes a living being to 

 remain inactive or dormant, with a suspension of all vital 

 functions. Eggs will remain sound and well preserved for a 

 long time before hatching. Rotifers have been desiccated in 

 heated sand, and revived by moisture, a score of times in suc- 

 cession. The hybernation of bears, frogs, and other animals 

 is a well-known phenomenon. The seed from the hand of an 

 Egyptian mummy has been planted after 3,000 years, and 

 produced perfect ears of wheat. Syncope is sometimes so 

 complete that life becomes dormant. There is no circulation, 

 respiration, nor motion. Cases of trance and catalepsy are 

 similar, and premature burial has occurred. Among Indian 

 fakirs instances of voluntary syncope, or human hybernation, 

 have been witnessed under the strictest precautions against 

 fraud. One was buried for six weeks, and another for ten 

 days. 



7. DEATH. 



Death is the cessation of vital power, to which disintegra- 

 tion and chemical decomposition succeed. In our view life 

 is not synonymous with spiritual existence, but the result 

 produced by the union of matter with spirit. Life has no real 

 existence apart from living matter more than motion can exist 

 without a moving substance. Life is propagated from one 



