STRUCTURE 



49 



ostia, and passes out through the arteries to circulate through 

 the organs of the body and to return by the ostia. 



The two figures below (Figs. 29 and 30) show the position of 

 the arteries and the ostia in a single segment of the body. The 

 heart is too small and delicate to be seen with the naked eye ; it 



Fig. 28. — Lithobius dis- 

 sected. (After Vogt 

 and Yung.) 



«, antennae. 



b, poison claws. 



c, brain. 



d^ salivary glands. 



e, legs. 



/, nerve cord. 



(7, Malpighian tube. 



h, Malpighian tube. 



4, vesicnla seminalis. 



j, accessory gland. 



k, accessory gland. 



I, testis. 



w, thigh gland. 



»!, digestive tube. 



therefore requires the aid of the microscope. A freshly-killed 

 animal was therefore taken and prepared in the manner known 

 to all microscopists, and extremely thin slices or sections cut 

 horizontally from its back. One of these sections cut the whole 

 length of the heart in one segment, which was accordingly drawn 

 under the microscope (Fig. 29), and shows a longitudinal hori- 



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