THE MICROSCOPE. 15 



Trichina sjnralis, a little spiral worm, which is genoratod in the 

 muscles of unwholesome pork, and is the cause of a frightful 

 disease if taken into the human body. It is for this reason, I 

 should perhaps mention, that it is so very necessary pork should 

 be always thoroughly cooked, or this animalcule is very tena- 

 cious of life, and will live through any but the fiercest heat. That 

 troublesome disease called ringworm is now known to be of vegetable 

 origin, consisting of a fungoid growth ; and the same may, to a certain 

 extent, be said of the thrush to which infants are so liable, and even 

 of diptheria. By the aid of the microscope it was discovered that all 

 things, animal and vegetable alike, are but a conglomeration of cells. 

 In the lower forms of life, each individual cell may be considered 

 perfect in itself, forming sometimes the entire individual, and capable 

 of independent life; in man and the higher animals the whole complex 

 organisation is gradually developed from the multiplication and secre- 

 tion of a single cell ; this, however, is far too vast and abstruse to be 

 more than alluded to in a fugitive paper like the present. Another 

 very interesting result of microscopic discoveries is the curious meta- 

 morphosis or transformation that goes on in the lower animals during 

 the difierent stages of life. We are all familiar with the change which 

 takes place from the tadpole into the frog ; but this, which we are 

 accustomed to consider an exception, appears rather to be the rule in 

 the lower organisations. I shall show you presently the larva of the 

 Mayfly, swimming and diving through the water like some ugly little 

 fish, and as unlike the light aerial fly which it ultimately becomes as 

 any two objects can be. Again, there is not much similarity between 

 a crab and a barnacle, yet in their earlier stages they are like Pompey 

 and Caesar, very much alike, both very much like the little water flea. 

 Indeed the very youthful crab was at one time considered and described 

 as a perfect adult animal of the water-flea class ; it must therefore be 

 quite impossible for a parent to know its own ofispring. 



The wonders which reward even a superficial knowledge of the micro- 

 scope are far too numerous to be alluded to in the limits of this paper; 

 for what can be more interesting than to watch the circulation of the 

 blood corpuscles in the living animal, and then to compare it with the 

 analogous process which goes on in plants, and is so well seen in the 

 Valisneria, &c. ? What more wonderful object in nature than the com- 

 pound eyes of many of our common insects, which are made up of hun- 

 dreds and thousands of separate eyes placed side by side, each eye 

 provided with iris, retina, and optic nerve ? The common fly is pro- 

 vided with no less than 4,000 eyes; while the cabbage butterfly has 

 17,000, the dragon-fly 24,000, and the Mordella beetle no less than 

 25,000. To the zoologist the assistance of the microscope is invalu- 

 able. By its aid he can determine from the minutest portion of bone 

 or tooth, not only the natural family, but the genus and species to 

 which its animal possessor belonged. The geologist again is not less 

 indebted to this wonderful instrument, for by its aid he is able to 



