120 Transactions of the Royal Microscopical Society. 
condition required for the subservience of other purposes, such as 
the preservation of the normal constitution of the blood, as well 
as the nutrition of the various tissues. 
Changes in the substance and form of the coloured blood- 
corpuscles of Man, similar to those above described, and which 
may be detected by the aid of the microscope, occur in various 
pathological conditions of the system. Although some attempts 
have been made by several pathologists to study these changes, no 
definite results have to my knowledge hitherto been obtained. The 
cause of this seeming failure, however, evidently depends on the 
difficulty attending the investigation of this subject, and I entertain 
no doubt as to the final success of these studies, if conscientiously 
and steadily pursued. For a number of years I have occasionally 
directed my attention to this subject, and have become convinced 
that changes in the form and character of the coloured blood- 
corpuscles of Man, which may he detected by microscopical exami- 
nation, do occur in pathological states of the system ; hut as my 
observations were confined to only a few diseases, as yellow fever 
and rheumatism, and were not made systematically, I shall forbear 
entering upon this subject at present. After I shall have accumu- 
lated additional facts to those already obtained, and on a more 
extended scale, I hope to present them in proper form to the 
profession. 
