96 Malpighi and the Physiology [lect. 



veins, the old term of the artery-like vein, and the vein-like 

 artery having by this time become obsolete) winding over the 

 air vesicles, but he could not as yet (he was so far working 

 chiefly on the lungs of dogs) satisfy himself on the point 

 whether or no the blood escaped from the minute arteries into 

 empty spaces whence it found its way into the minute veins. 

 A little later he turned his attention to the simpler lung of the 

 frog, and in this he had the happiness, calling into his aid the 

 microscope, to see that minute but definite channels, the 

 channels which we now call capillaries, joined the endings of 

 the minute arteries to the beginnings of the minute veins. 



In his second epistle to Borelli, after describing, under the 

 heading ' I see with my own eyes a certain great thing,' the 

 appearances presented by the lung of the living frog extruded 

 after the laying open of the body, which organ he says "is 

 " nothing else than a sort of membranous bladder which at first 

 " sight seems to be sprinkled over with very little spots 

 "disposed in an orderly fashion like the skin of the dog-fish, 

 " commonly called Sagrino," he thus continues : 



" Something still more wonderful than the above appearances 

 " which relate to mere structure and build is disclosed by 

 " microscopic observation. For, while the heart is still beating, 

 " two movements contrary in direction though accomplished 

 " with difficulty are observed in the vessels so that the circu- 

 " lation of the blood is clearly laid bare ; and indeed the same 

 " may be even more happily recognized in the mesentery and in 

 " other larger veins contained in the abdomen. And thus by 

 "this impulse the blood is showered down in minute streams 

 " through the arteries, after the fashion of a flood, into the 

 " several cells, one or other conspicuous branch passing right 

 " through or leaving off there, and the blood, thus repeatedly 

 " divided, loses its red colour, and, carried round in a sinuous 

 " manner, is poured out on all sides until it approaches the walls, 

 " and the angles and the absorbing branches of the veins. 



" The power of the eye could not be carried further in 

 " the opened living animal ; hence I might have believed 

 " that the blood itself escaped into an empty space and was 

 "gathered up again by a gaping vessel and by the structure 



