64 PROFESSOR E. RAY LANKESTER. 



blood removed from the blood-vessels. But the inference to be 

 drawn from, tl Is observation is not that the nucleus is not present 

 in the living corpuscle, but that the refractive properties of the 

 albuminous matters comprising the nucleus and the body of the 

 corpuscle are such as to make it difficult to define with 

 the microscope the albuminous nucleus embedded in the albu- 

 minous body. A change in refractive properties of the substance 

 of either or of both parts of the corpuscle allows us to define 

 the hmits of the nucleus. 



The same is true with regard to the cell-parasite Brepankl'mm, 

 which (as I have myself observed and as Dr. Gaule admits) 

 becomes visible within a red blood-corpuscle treated with "3 per 

 cent, salt-solution, just at the same moment and in the same 

 degree as does the nucleus. In the normal condition of the red 

 blood-corpuscle a minute Drepanidium, embracing in crescent 

 form one end of the nucleus, escapes observation — is in fact 

 invisible, just as is the nucleus itself — owing to the refractive 

 index of its delicate substance and that of the body of the cor- 

 puscle being identical.^ 



Dr. Gaule's advocate would, however, reply that he has 

 carried his case further than this. He states that taking a drop 

 of blood from a Frog known to yield Brepanidium he added at 

 once to it osmic acid or other fixing reagent and that on sub- 

 sequently staining this blood-preparation though he obtained the 

 nuclei well coloured and well defined — he could detect no 

 Drepanidia. On the other hand, a drop of blood from the same 

 Frog — which wasjirst treated with a '3 per cent, solution of 

 sodium chloride — yielded plenty of Drepanidia, which could be 

 fixed with dilute acid and stained. 



In reply to this, I can merely say that I have obtained the 

 Drepanidia in Frog's blood and spleen-pulp, which was not 

 exposed to the action of sodium chloride, but was spread when 

 fresh in dilute osmic acid. Further, it is admitted by Dr. 

 Gaule that the Drepanidia do exist in the living Frog indepen- 

 dently of any experimental treatment of the blood. His 

 differential experiment is inconclusive, because it is possible that 

 one drop of the Frog's blood might contain few or none of the 

 parasites, whilst a second drop (that treated with the salt- 

 solution) might contain many. It is also by no means impro- 

 bable that a previous treatment with salt-solution, as compared 

 with the immediate treatment of a drop of blood or a piece of 



I It is a fact tliat parasitic Micrococci and Bacteria escape observation 

 iu the celis of iiving or fresh tissues in this way, and it is worthy of note 

 that Lieberkiihn calis the faliciform corpuscles of the naviculoid spores 

 found by him in the Frog's kidney " diaphanous rods." They are, in fact, 

 very deUcate and transparent objects when alive. 



