372 DETAILED SYNTHESIS. 



tissue, and, as far as can be judged, float in the Blood independently of 

 any nervous influence. If, however, they were massed as a gland, they 

 would form the essential part of it, and if their action is no higher than 

 that which exists in the plant, there would be no necessity for nervous 

 influence. Hence they may be considered the simplest form of a gland, 

 dissolved, so to speak, in*fbe Blood ; or they may be looked upon as 

 floating plants, and, as their office is modificatory, they are correctly 

 classed under the above head. If the cells need nervous influence, it 

 may be received as they pass through the capillaries of the nervous 

 centres. 



1158. Inf. Since the Blood in the body weighs not less than 

 twenty pounds, IF THESE CELLS HAD BEEN MASSED, constituting when dry 

 one tenth, and distended one half the bulk of the Blood, they alone 

 would have weighed ten pounds, and with the other tissues of an organ, 

 at least fifteen pounds. Where in the body could this have been conve- 

 niently located ? Observe the beauty of the arrangement by which this 

 immense gland is dissolved hi the Blood. Also notice, that the blood- 

 cells exceed in weight all the other secretory tissues collectively ! 



1159. Remark. SINCE THE BLOOD-CELLS HAVE THE NATURE OF 

 PLANTS, it is PROBABLE that the influence of the sun's light and heat as- 

 sists in perfecting them and their action, especially as it is certain that 

 an active circulation of Blood through the skin, and a free exposure of 

 it to the influence of the light, and heat, and chemical rays of the sun, is 

 essential to perfection pf health, and always conducive to its improve- 

 ment, while the opposite conditions, viz., feeble circulation in the skin, 

 cold, and darkness, is sure to deprave health, however good. 



11 GO. Inf. WINDOWS SHOULD BE large and numerous, especially in 

 a school-house, and every room hi a house should be so constructed as 

 to receive directly the rays of the sun. 



1161. Remark. ALL WINDOWS SHOULD BE DOUBLE IN WINTER, that 

 they may preserve the heat that flows in from the sun, as well as that 

 produced within by artificial means ; not with the object of keeping out 

 the cold air, an abundance of which, for purposes of ventilation, should 

 be properly introduced, and can be afforded, if windows are double, for- 

 rooms are chiefly cooled by heat passing through the glass itself. Dou- 

 ble windows arc a great economy. 



Lymphatic Glands. 



1162. LYMPHATIC GLAITDS are small bodies, about 

 the size of grains of wheat, and exceedingly numerous in 



1158. "What ? "What previous paragraphs describe blood -cells ? 1159. "What 

 ? 1160. What should 1181. Why should ? 1162. What are f 



