422 CHAMBERLAIN AND VEDDER. 



We believe that we can point out the nature of these bodies, and that 

 we should do so, not only because two papers have been published on 

 the subject, but because it has come to our knowledge that other inves- 

 tigators have been misled by them. Therefore, a statement of their 

 true nature may simplify investigations in the future. 



These peculiar bodies were first observed by one of us in 1907 while 

 studying the blood of dengue, and before the publication of the paper 

 by Horrocks and Howell. They were at first thought to be parasites 

 associated with that disease, but further study showed that they were 

 frequently present in normal blood.. Subsequently they were found again 

 in specimens from various pathologic conditions, and from different parts 

 of the body, and the idea was finally suggested that they were artefacts 

 in the glass slides. Search of a number of plain unstained glass slides 

 having no specimens on them revealed the fact that these bodies could 

 be found on many. On such unstained slides the bodies have the same 

 moi'phology, but are without coloration. When the glass slide is pre- 

 viously stained with a little Wright's stain, as though staining a blood 

 film, the bodies take on exactly the appearance described and accurately 

 depicted by Horrocks and Howell and by Balfour. 



The X-bodies in these two papers are, therefore, artefacts of some 

 sort, present in certain of the glass slides for microscopic use. We think 

 that they are found more often in old slides which have been used several 

 times, and have been kept for some time in the Tropics. We believe 

 that anyone finding the X-bodies in a preparation can readily verify our 

 statement by staining and examining some of his slides on which no 

 smear has been made. The bodies are not in the stain, because they 

 may be found in unstained preparations. 



Other facts that confirm these observations are: 1. The X-bodies have 

 been found on slides made under a great diversity of conditions from 

 both men and animals, including the blood from cases of malaria, un- 

 determined fever, urticaria and dengue, and normal blood in the human, 

 and also the blood of oxen and rabbits and the liver of oxen. We have 

 observed them in slides containing scrapings of skin mounted in liquor 

 potasspe. 2. In the same case the bodies are not found constantly, but 

 are only seen in a few out of many smears, although they are usually 

 numerous in the particular slides in which they are obsei'ved. If present 

 in the circulating blood, they should be found on all or nearly all the 

 slides examined from the case at the same time, though not necessarily 

 in large numbers. 3. So far as we are aware the bodies have never 

 been detected anywhere except in smears or preparations made on glass 

 slides. 



As further evidence in favor of the X-bodies being in the surface of 

 the slide we performed the following experiment : 



