iv] of Glands and Tissues. 99 



other structures, and it soon became acknowledged that the 

 circulation was a more complete mechanism even than Harvey 

 had supposed, that the blood flowed in wholly closed channels 

 from the heart through arteries, capillaries, and veins back to 

 the heart again. A sound view of the processes of nutrition 

 thus became possible, and it was Malpighi who first found the 

 missing link in the chain of Harvey's discovery. 



In a little tract on the omentum, fat, and adipose ducts (Be 

 omento, pinguedine, et adiposis ductibus) published four years 

 later, in 1665, in company with three other tracts of which I 

 am about to speak, Malpighi records an observation which shews 

 that he had hit upon another discovery touching the blood ; 

 but he failed to lay hold of the meaning of what he saw. Up 

 to this time the redness of red blood had been supposed to be 

 diffused over the whole fluid. Malpighi in describing the fat-cells, 

 of which he found the fat of the omentum to be composed, states 

 that, using the microscope, he fancied he saw small flat red cells 

 in the mesenteric blood-vessels of the hedgehog (his anatomical 

 histological studies were carried out on almost all manner of 

 animals). This is what he says : 



"And I myself in the omentum of the hedgehog in a 

 "blood vessel which ran from one collection of fat to another 

 "opposite to it, saw globules of fat, of a definite outline, 

 "reddish in colour. They presented a likeness to a chaplet 

 "of red coral." 



He mistook however the nature of what he saw. What 

 evidently were blood corpuscles he thought to be fat cells 

 passing from the fatty tissue into the current of the blood. 



Meanwhile in thus seeing red blood corpuscles he had been 

 anticipated by the great Dutch observer of minute structures, 

 Johannes Swammerdam of Amsterdam. That great work of 

 patient conscientious industry, Biblia Naturce, though not 

 published until 1738, and then by Boerhaave, long after the 

 author's death in 1680, contains the record of an observation 

 made so early as 1658, seven years before the appearance 

 of Malpighi's tract. Speaking of the blood of the frog he 

 says: 



" In the blood I perceived the serum in which floated an 



7—2 



