OF THE TISSUES. 1 



from the parallelism of the muscular tissue; not so 

 straight as the one nor so convoluted as the other. Ob- 

 servers differ in respect to the size of these globules ; 

 some say they are one four thousandeth, others, one six 

 tbousandeth, and others still, one eight thousandeth part of 

 an inch in diameter. But what renders these observa 

 tions peculiarly interesting is the discovery made par- 

 tially, indeed many years ago, but recently confirmed by 

 many new and curious facts that if vegetable or animal 

 substances be macerated lor some time in water at a 

 moderately warm temperature, the fluid will be found, 

 after a certain time, sw r arming with animated bodies too 

 small to be within the reach of unassisted sight. They 

 have been styled Infusoria because they have been gen- 

 erally observed in vegetable infusions. The simplest 

 form of these creatures is that of a ti ansparent globule, so 

 small that it appears to be a mere animated point. They 

 have the same Ibrm and magnitude as the elementary 

 globules of which the primitive tissues are composed. 



Emily. But how is it known, Dr. B., that they do 

 really possess life ? 



Dr. B. That fact is inferred by their rapid and un- 

 eeas : !)g motions which have every appearance ol being 

 sjtonianeous. 



Emily. And yet it is so clear that these motions may 

 not be occasioned by heat, electricity, or some other 

 physical cause ? 



Dr. B. We cannot say but they are yet so long as 

 the agency of no physical cause with which we are ac- 

 quainted can be demonstrated to be present, we have no 

 right to affirm its existence, if the fact of their vitality be 

 strengthened by considerable evidence. For microsco- 

 pical observations have made us acquainted with other 

 minute beings differing from these simple globules only 

 by a slight addition to their structure. In one kind this 

 difference consists in the addition of an appendage in 

 the shape of a tail. Next above these in the scale of 

 complexity, is another kind which seem to consist of 



