126 THE MICROSCOPIST. 



digestive system of Melolontha. B, is that of Blatta Ameri- 

 cana (American Cockroach), a is the oesophagus, b the crop, at 

 the bottom of which is the gizzard, c, consisting of several 

 teeth arranged like a funnel, with the apices of the teeth in 

 the centre. Another view of the gizzard is seen at C. The 

 bile-tubes or liver are shown at d, and the salivary glands at e. 

 Attached to the stomach, just below the gizzard, are eight 

 blind sacs, /, the use of which is unknown, but is supposed 

 to be analogous to the pancreas. 



The salivary glands, stomach, &c., should be generally 

 mounted in fluid. Gizzards may be put up in balsam. The 

 gizzard of a cricket is an interesting object; it has over two 

 hundred teeth. They may be prepared by making a longitu- 

 dinal incision and spreading out to dry ; or by inflating, after 

 the gizzard has been cleaned of its contents, by means of a 

 small syringe. After drying in the latter mode it may be cut 

 in two, so as to show the parts in their natural position. 



The Nervous System consists of two medullary cords or 

 threads, which run along the middle of the abdomen inside, 

 exhibiting a series of knots or ganglia. 



Fig. 37 exhibits the nervous system of a caterpillar, from a 

 preparation of Dr. Goadby's. The double ganglion, A, seems 

 to occupy the place of the cerebellum, and B, also double, and 

 transverse to the others, answers to the cerebrum. C, C, the 

 two cords uniting them. E, the space through which the 

 oesophagus passes. F, F, F, the ganglia which unite the two 

 cords. The distribution of the nerves through the body is 

 from the ganglia. The apparent exception to this, as at D, 

 are proven, by Dr. Goadby's investigations on the Limulus, to 

 be, in fact, arteries, as they have been injected. Coagulated 

 insect blood is white, hence they appear like nerves. 



4. The Circulatory System is placed along the back, and 

 consists of a heart or dorsal vessel ; which is a tube divided 



