VOL. XV.] PHILOSOPHICAL TRANSACTIONS. 123 



stance, whereof these parts chiefly consist. To which may be added that there 

 were several particles mixed, about as large as ^ of a blood globule, which were 

 not transparent. We may perceive that the cortical parts in many places enter 

 deep into the medullary, but if we diligently search into them, we shall find 

 them as full of blood-vessels as the outside. Besides these very thin blood- 

 vessels, there are other vessels in the brain, so thin, that I conceive a round 

 body, although divided into above 1000 parts, could not pass through them. 

 And it is to be noted, that in these observations are mentioned only those blood- 

 vessels, which are as thick or thicker than a hair of the head. 



In the medullary parts of the brain were contained irregular globules of dif- 

 ferent sizes, some of them as large as a globule of our blood, and some larger, 

 seeming to consist of a thin transparent oil-like substance; these are here in 

 such numbers, chiefly where the medulla spinalis begins, that they seem to 

 compose the greatest part of the brain. This great number of transparent glo- 

 bules causes a white colour, and they were yet so fast joined to each other, that 

 some would be drawn out to twice their natural length, and then seemed to me 

 as if they were kept together by net-like threads. This made me think, that 

 the smallest branches of the blood-vessels might encompass these globules as 

 the small horizontal vessels, in some kinds of woods give way to the great per- 

 pendicular vessels, and wind half about them. And I was confirmed herein, 

 when I perceived many of the aforesaid vessels appeared clear in the middle, and 

 brownish on both sides; but more brown when I had torn the globules asun- 

 der, and laid the thin thread-like parts by themselves. In fine, the medullary 

 parts of the brain appeared often like a fisher's net, between each of whose 

 meshes was placed a very pliable ball-like substance, which changed its figure 

 into round or oval, according as the said meshes were stretched one way or 

 other. Moreover the said medullary parts consisted of a very great multitude 

 of very small globules, and some clear thin matter. 



I observed also the brains of a sheep, and perceived in the cortical parts, a 

 great multitude of extremely thin blood-vessels, containing some of the sub- 

 stance which makes the redness of the blood. The cortical part of the brain 

 had also white streaks or lines, thinner than a hair of the head, which to the 

 naked eye were invisible. I have also perceived brown streaks running through 

 the medullary part of the brain, which were only caused, as I conceive, by 

 there being but few or none of those transparent globules there placed. 



Afterwards I carefully examined the brain of an ox, and satisfied myself that 

 the vitreous and very transparent matter, which makes up most of the cortical 

 part, consisted of nothing but extremely thin streaks or vessels, which were 

 nearly joined together; but at another time I could not fully satisfy myself con- 



B 2 



