THE PAGE OF NATURE. 167 



The existence of life within life, or of a flora within 

 the bodies of living animals, is one of the most extra- 

 ordinary facts which the microscope has revealed to us. 

 Upwards of ten species of entophytes have already been 

 discovered parasitic upon man, two of which belong to 

 the confervse : the one Lewenhoeck's alga, a minute fila- 

 mentous plant growing between the interstices of the 

 teeth, and covering the roof of the mouth in abnormal 

 conditions of the body ; and the other the Sarcina ven- 

 triculi of Goodsir, a free unattached plant existing in 

 rare cases in the stomach, and counteracting, by its ex- 

 treme minuteness and its very rapid reproductive power, 

 the expulsive efforts of that organ. Man, however, is 

 less infested by these entophytes than any other animal, 

 on account of the cooking process to which his food is 

 subjected, which effectually destroys the germs of para- 

 sites, and his high degree of organic activity, which is 

 unfavourable to their development. Animals of feeble 

 vitality and sluggish habits, using solid innutritions food 

 difficult of assimilation, and therefore remaining long in 

 the alimentary canal ; or animals swallowing their food in 

 large morsels, to which the germs of plants may adhere, 

 are rarely, if ever, free from these entoparasitic plants, 

 which, however, when few in number, or not of excessive 

 size, are quite harmless. They are found principally in 

 those portions of the body which are easy of access from 

 without, such as the stomach and intestinal canal, and 

 where, of course, all the indispensable conditions for the 

 maintenance and reproduction of such life exist. In ac- 

 counting for their origin the opinion may be hazarded, 

 either that their germs belonged to plants growing ex- 



