54 PROCEEDINGS OF SOCIETIES. 



contaiuing ova, so that it might be regarded as an object worth a place 

 in the cabinet. 



The thanks of the Society were voted to Mr. Beck for the present. 



The Secretary said that they were very much indebted to Mr. Baker 



and Mr. How, for the loan of a number of microscope lamps for use 



at their Scientific Evening on the preceding Wednesday ; the thanks 



of the Society were accordingly voted to those gentlemen. 



Dr. Lawson said he had to exhibit an invention of M. Hayem, 

 made by M. Nachet, of Paris, and termed a Hematimetre, for the 

 purpose of estimating the amount of red corpuscles in the blood. It 

 was not strictly speaking a novel instrument, but it was new in form. 

 Various apparatus had from time to time been devised for the pur- 

 pose, but none of them were very convenient, inasmuch as they all 

 required several hours' interval for the investigation, whereas tbe one 

 before the meeting was much more simple and more easily used. It 

 consisted in the first place of a slide having cemented to it a piece of 

 glass with a hole cut in it, and then reduced to a certain level so as 

 to have a depth of exactly one-fifth millimeter. In the eye-piece of the 

 instrument there was a sort of micrometer, also arranged so as to give 

 a view of only the space of one-fifth millimeter, the object of this being 

 to procure for examination exactly the volume equal to the one-fifth of a 

 millimeter cubed. If, however, they were to take exactly that amount of 

 blood for examination, they would find such an agglomeration of cor- 

 puscles that it would be impossible to estimate them ; but for the 

 purpose of being able to enumerate them, M. Hayem took a gradu- 

 ated tube, and having measured 2 cubic millimeters of blood and 

 placed this in a small vessel, he measured into another vessel half a 

 cubic centimeter of serum, and then having put the blood into it he 

 stirred them up so as to make the mixture complete. He then placed 

 sufficient fluid from this mixture in the cavity of the slide to exactly 

 fill it, and jnit it under the microscoiie. Then by focussing the 

 instrument upon it, it was possible to readily count the number of cor- 

 puscles in tbe one-fifth of a millimeter cubed. He (Dr. Lawson) had 

 endeavoured to count them in that way, and found the number in the 

 ruled space to be 142 ; and by multiplying this number by 125 and 

 then by 251 (which corresponded to the quantity of serum employed 

 + 1) he obtained 142 X 125 x 251 = 4,455,250, as the number of 

 corpuscles in an ordinary cubic millimeter of blood, 



Mr. Cbarles Brooke said that if the amount were one-fifth cubic 

 millimeter, then it would not do to multiply by 125, the 142 should 

 be in that case multiplied by 5 instead ; but if a cube of one-fifth 

 millimeter were intended, the result as stated would be correct. 



Dr. Lawson said that he had intended it to be understood as a 

 cube of one-fifth niillimetor. 



The Secretary said they had a microscope brought for exhibition 

 by Mr. Crouch, the peculiarity of which was that it was furnished 

 with an arrangement for exactly centering the stage for the particular 

 objective which was being used, and he called upon Mr. Crouch to 

 further explain tbe imi)rovement to the meeting. 



IVIr. Crouch thought it scarcely necessary to say anything further, 



