CELLS, THE ESSENTIAL ORGANS OF LIFE. 25 



entire animal consists of but one single cell, [the Mo- 

 nads)', and others, in which each individual is but a 

 cluster of such cells arranged in a definite manner. 

 These mere aggregations of simple cells perform all the 

 functions of animal life, namely, the maintenance of a 

 particular form for a certain duration of time, the ela- 

 boration of materials of support from food, locomotion, 

 and the continuation of the species; hence, these ani- 

 mals, like the simplest plants, may be divided without 

 destroying their vitahty, and every part may become a 

 perfect individual*. To this class belongs the Hydra, 



* Since, therefore, the extreme point to which we can trace animal or- 

 ganisation is a cell, and all the important processes by which the fabric 

 is renovated and maintained are performed by the agency of cells en- 

 dowed with specific properties, — some secreting the bile, others the fat, 

 others the mucus, and so forth, — it follows, that, upon the integrity of the 

 structure and function of a cell, or of a cluster of cells, may depend the 

 maintenance of health ; in other words, that the first germ of disease may 

 arise, and for awhile lie hidden, in these integral elements of animal or- 

 ganisation. Hence, we can understand how mental emotions, by disturb- 

 ing or weakening the vital influence transmitted by the nerves to the cells 

 of any particular organ, may impair the structure and vitiate the secretions, 

 and ultimately induce extensive local disease, long after the cause of the 

 physical derangement has passed away, and is forgotten. Of the truth of 

 this remark, pulmonary consumption, alas ! affords eveiy day the most un- 

 equivocal and melancholy proofs. But the Tree of Knowledge yields good 

 as weU as evil fruit ; and, if recent microscopical discoveries are calculated 

 to alarm the timid, by shewing what shght causes may lay the foundation of 

 fatal diseases, on the other hand, they encourage the cheering hope, that, 

 by patience and perseverance, we may at length learn how to detect the 



