596 
DR. T. WILLIAMS ON THE BLOOD-PROPER AND 
In this communication it is my desire to restrict myself chiefly to the demonstra- 
tion of the corpuscular or morphotic elements of the fluids, postponing- to a future 
occasion the attempt to apply the results of these researches to the problems in com- 
parative physiology which they promise, satisfactorily, to resolve. 
As far as my inquiries into the historical literature of this subject have extended, I 
may affirm that no systematic definition of the real nature of the circulating fluids, 
in the lowest orders of animals, has ever yet been attempted in physiological science. 
The true mechanism of nutrition in zoophytic, radiate and annulose organisms, has 
never yet, at the hands of zoo-chemists, received a satisfactory explanation. The 
organic fluids have been subjected in no one of their characters to a full and ade- 
quate investigation. 
They have been permitted to remain, up to this time, almost entirely undescribed 
and uncomprehended. 
To these condemnatory observations, exception must be made in favour first of 
Agassiz and Milne-Edwards. Obscure hints, tending to the right track of study, 
have been thrown out by the former naturalist, and by the latter, certain generalized 
views have been propounded which serve only to indicate the correct direction of 
inquiry. Agassiz* remarks, “Instead of the three conditions of chyme, chyle, and 
blood, which the circulating fluids of the Vertebrata undergo, the blood of that class 
of the Invertebrata which I have particularly studied, the Annelida, is, according to 
Wagner, simple chyle, coloured chyle ; the receptacles of chyle in different parts of 
the body are true lymphatic hearts, like those found in the Vertebrata : this kind of 
circulation is found in the Articulata and Mollusks, with few exceptions, some 
Echinoderms, &c. In the Medusae and Polyps, instead of chyle, chyme mixed with 
water is circulated : this circulation is found in some Mollusks and intestinal worms ; 
it may be seen plainly in Beroe." It will be subsequently shown that these boldly 
propounded generalities seldom approach the truth of nature as established by 
practical observation. 
The admirable researches of Milne-Edwards'|' were chiefly directed towards the 
determination of the mechanism of the circulation, rather than to the composition of 
the fluids. His inquiries were principally limited to the Annelida, Mollusca and 
Crustacea. With him originated the generalization, that “in no Mollusk does there 
exist a closed system of blood-vessels ; that in the Bryozoa or Polyzoa, the initiatory 
class to the Mollusca, neither heart, arteries nor veins are found, the nutrient fluid 
being contained in the great visceral cavity, in which the organs of digestion are 
suspended ; that in the Molluscoid Tunicata a heart and a system of blood-vessels 
exist only in the branchial portion of the body, the abdominal or visceral circulation 
being conducted by means of cells or lacunae of uncertain direction and without any 
* Silliman’s American Journal for July 1850. 
t Annales des Sciences Naturelles, Sdrie 3“®. t. iii. 280 (1845). 
