Inquiry into the Nature and Properties of the Blood. 189 



prospect of the circulation through numbers of small vessels. 

 But nothing can show it finer than an exceeding small newt 

 of this water-kind which sometimes may be found less than 

 an inch long, and so transparent that the blood may be seen 

 running in all directions, not only through the vessels of the 

 tail, but throughout the whole body. In the fin-like processes 

 situated just below the head the blood is seen coming along 

 an artery to the extremity, and then immediately returning 

 towards the heart again, through a vein that lies close and 

 parallel thereto, and with which its communication is very 

 apparent. This affords a charming sight, and may be viewed 

 by the third or fourth magnifier; for the globules of the 

 blood in ncvots are larger than in any other creature I have 

 examined, and are fewer in proportion to the serum or water 

 they float along in." To which he also adds, that the figure 

 of them, as they^are carried along the vessels, changes in a most 

 surprising manner. 



The recently produced tadpole being very transparent, is a 

 good object for discerning the pulsations of the heart together 

 with the circulation of the blood in every part of the body ; 

 the skin and transparent parts of muscles ; the furthest joints of 

 the hinder legs of little crabs ; the legs and tails of shrimps ; the 

 transparent legs and head of several small spiders, and the cur- 

 rent of the blood may be clearly discerned both in the veins 

 and arteries. Mr. Leeuwenhoeck found the globules in various 

 kinds of fish, — as the perch, trout, and salmon, — to be flat and 

 of an oval figure, as also in some birds. The serous part of the 

 blood in fish and aquatic animals is in greater proportion to 

 the red particles than in animals or man, whilst the particles 

 themselves are larger. 



In viewing several of the above objects the blood may 

 often be observed passing through vessels so minute, that its glo- 

 bules cannot glide along otherwise than single, and squeezed 

 into oblong forms : yet a hundred of such globules, if placed 

 close to one another in a row, would not ecjual the length of 

 the diameter of a large grain of sand. Some experiments 

 which were made by Mr. Baker, and his friend Dr. Alexander 

 Stuart, ))hysician to the c|ueen consort of George the Second, 

 with a sohir microscope of a peculiar construction, we cannot 

 omit to mention ; though for accurate information we allow 

 such a juethod as they adopted to be in many respects defi- 

 cient; but as this deficiency does not affect the point under 

 consideration, their experience may be regarded as extremely 

 satisfactory. " Our object," says Mr. Baker, " was a frog, whose 

 liini)s l)eing extended and liislened on the frame, we opened 

 the skin of the bellv hum near the anus to liic throat; then 



