90 HALF-AN-HOUR AT THE MICROSCOPE. 



Section of Small latestine of Mouse (PI. III., Upper portion). 

 In this preparation some interesting points in the blood-supply are 

 well shown. The part is that which succeeds to the stomach ; it 

 is in it that the absorption of nutrient materials, from food received, 

 principally occurs. To increase the absorptive surface, it is raised 

 into innumerable finger-like processes called "z^////." Certain 

 smaller vessels may be seen in the line of axis of the villi, which 

 are the Arteries; there is also one vessel of larger calibre by which 

 the blood is carried away — the Veins. Proceeding across the villi, 

 and constituting a network over and a little within its surface, are 

 finer vessels, the capillaries ( Capillus, a hair). On reflection it will 

 become evident how admirably such a sponge-like arrangement is 

 adapted to the purposes of an organ, alternately turgid through 

 the stimulus of present food, and flaccid during intervals of absti- 

 nence. The surface of the villi is covered with conical epithelium 

 cells, whose office is to absorb the liquid aliment, and to pass it 

 on to channels excavated in the villi, the lacteals (lac, lactis, milk), 

 from the milky appearance of their contents. The lacteals unite, 

 and receive the name of lymphatics, and the contained fluid is 

 eventually poured into the great veins of the neck on the left side, 

 just above the heart. In the lungs a wonderful change takes place, 

 the " chyme " becoming changed into fully formed blood. 



Cheyletus eruditus (PI. III., Figs. 1-4). — R. Beck was not the 

 first to discover this insect. It will be found mentioned in an 

 Enumeration of the Insects of Austria^ by Schrank, published 

 towards the close of the last century' (1792, circa), and afterwards 

 by Latreille, in the Natural History of Crustacea and Insects 

 (1806 — 9). R. Beck found it independently in 1866, and though 

 he did not know what he had got, to him belongs the merit of 

 accurately observing its life-history, as well as carefully describing 

 and figuring it. Mclntire's paper in Sciefice Gossip partakes some- 

 what of the sensational, and his account is rather confused in parts. 

 The figure at its commencement is thought by M. C. Cooke to 

 represent, probably, C. verrutissimus^ Koch. As to oviposition, 

 I doubt the weaving of threads around the eggs to retain them in 

 their places, either from the mouth or elsewhere, and think there 

 must be an error of observation. By R. Beck's description the 

 eggs are attached by a short thread of condensed mucus to the 



