VOL. XII.] PHILOSOPHICAL TRANSACTIONS. 403 



red. And these greater globules which compose the brain, are very irregular 

 in respect of what those of the blood are. 



I remember that having formerly observed the brain of a duck, I then judged 

 that the appearance was caused only by the close union which the globules had 

 to each other, and which changed into threads by a little stretching. But con- 

 tinuing my observations for almost a whole month together, I have seen plainly 

 the very great number of exceedingly small veins running through the brain; of 

 which I could not at first assure myself in the brains of beasts that they were 

 indeed veins, because they are difficult to discern: but coming to observe the 

 brains of cod-fish, I plainly saw those numerous vessels or veins which were 

 very clear, disseminating themselves by their small branchings, and being 15 or 

 20 times finer than a single thread of a silkworm. These small vessels or veins 

 I have seen in great numbers in a part of the brain not larger than a grain of 

 sand : besides I saw vessels filled with blood, or appearing red ; as also vessels 

 that had the thickness of a single thread of a silkworm and very clear. Pur- 

 suing these observations about the brains of beasts, I was able very plainly to 

 represent to myself the vessels abovementioned ; and I could not without great 

 admiration behold them, partly by reason of their great number, partly of their 

 extraordinary subtlety; so that if one of the red blood globules were divided into 

 8 parts, and were of a firm substance, it could not pass any of these small 

 vessels. And the oftener I repeated my observations the plainer I could see 

 those manifold little vessels with their ramuscles, which were all very feeble, 

 and by the least touch broke asunder. 



Among the said globules, of which the brain partly consists, I have seen 

 blood globules, which may plainly be discerned from the brain-globules, especi- 

 ally by the perfect roundness which the blood globules had. These blood 

 globules I imagined came out of the sanguineous vessels which run through the 

 brain, and had been cut in pieces by the knife. 



Between the cortical and medullary part of the brain I can see little or no 

 difference, especially when I represent them before me very thin : only this I 

 noted, that the little veins or vessels which ran through the cortex were of a 

 dark and brown colour, whereas those in the medulla were clearer and more 

 transparent. 



I have seen in the brain, and most in the cortical part, such small sanguine- 

 ous red vessels, which came out of larger ones, that I cannot comprehend how 

 the globules could pass through them ; and when we see the blood globules 

 single, they have little or no colour, whereas on the contrary the blood in these 

 small veins was yet red : and the red colour even penetrated through the veins, 

 and coloured the neighbouring parts of the brain red. 



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