DISSECTING OBJECTS. 123 



pupa could be shown to be wrapped up in the caterpillar, and 

 the butterfly in the pupa. 



Those who look into the works of Swammerdam, will be 

 abundantly gratified, whether they consider his immense labor 

 and unremitting ardor in these pursuits, or his wonder- 

 ful devotion and piety. On one hand, his genius urged him 

 to examine the miracles of the Great Creator in his natural 

 productions; while, on the other, the love of that same All- 

 perfect Being, rooted in his mind, struggled hard to persuade 

 him that God alone, and not his creatures, was worthy of his 

 researches, love, and attention. 



In addition to the chapter on procuring objects, a few further 

 remarks on the internal anatomy of insects will not be out of 

 place. For the microscopic anatomy of other parts of the ani- 

 mal organization, the reader is referred to Chapter V. 



1. Tracheae, or Respiratory System of Insects. Respiration 

 in insects is effected by means of two great longitudinal ves- 

 sels or canals called tracheae, running along the sides of the 

 body beneath the outer integuments and muscles, terminating 

 in breathing pores (spiracles or stigmata). These pores or 

 spiracles are placed along each side of the body in terrestrial 

 insects, and are furnished with a beautiful mechanism to pre- 

 vent the admission of foreign particles. The tracheae emit an 

 infinite number of ramifications, extending to all parts of the 

 body, so that air circulates freely in every pa'rt. The tracheae 

 consist of an elastic spiral cartilage rolled up into a tube, 

 lined on each side with cellular tissue. In Fig. 35 the tracheae 

 of the larva of the Cossus ligniperda, or willow moth, is re- 

 presented. Along each side of the caterpillar are seen the 

 spiracles. 



To obtain the tracheae, &c., the insect should be placed in a 

 small trough with water, and be securely fixed to a loaded cork. 

 The body being laid open, next to the large viscera, the tra- 



