COUNTING THE BLOOD-CORPUSCLES 281 



of tissue lymph to the blood means another source of error, although in itself 

 not a great one. 



In spite of all these objections, which should be constantly borne in mind, 

 the clinical estimation of hemoglobin is of great value; in practice it is un- 

 questionably more important than all other methods of blood examination. 

 The decision of the most important question, whether the patient be anemic 

 or not, can only be made positively by a hemoglobin test. The physician 

 should accustom himself to look upon an examination of a patient as com- 

 plete only after the blood has been examined by the aid of a hemoglobinometer ; 

 then a surprisingly large number of persons will be found whose blood will 

 show quite a different condition from what might have been expected before 

 the examination from their general appearance. My estimation is rather too 

 low than too high when I say that fully one-half of those who are pale, who 

 have pale mucous membranes and cool extremities, and for this reason usually 

 designate themselves as " anemic," show a perfectly normal amount of hemo- 

 globin. Such persons do not suffer from an abnormal composition of the 

 blood, but from its abnormal distribution. That the- greatest differences in 

 regard to treatment will result from this in individual cases certainly requires 

 no further demonstration. I shall only point to the futility of many a treat- 

 ment by iron ; due to the fact that the treatment was begun without any indi- 

 cation for it, i. e., without proof of a diminution in the amount of hemoglobin. 

 A careful test of the amount of hemoglobin in the blood would in many cases 

 cause us to relinquish the iron treatment and lead to the use of other cura- 

 tive methods. 



In concliision I must add that a diminution in hemoglobin may occasion- 

 ally be discovered where the external appearances by no means indicate anemia ; 

 of course a correct estimate of the degree of anemia in such cases must depend 

 upon a test of the hemoglobin. 



The chief value of the clinical investigation of hemoglobin depends upon 

 the fact that it soon informs us whether and to what degree the blood may be 

 looked upon as anemic; from this we can determine whether to investigate 

 the blood for other changes or not. 



II. COUNTING THE BLOOD-CORPUSCLES 



For this purpose we use exclusively the Thoma-Zeiss counting apparatus 

 (Fig. 14). This consists of a pipette G with a mixing chamber E, in which 

 the one or ten per cent, blood dilutions are made; and of a counting chamber 

 D and c in which under the microscope 400 divisions may be recognized, each 

 containing -^-^^ c.mm. In counting the red blood-corpuscles the following 

 method is pursued : The blood is sucked up to a definite mark in the capillary 

 tube, and then diluted with a preserving iiuid. We use exclusively Hayem's 

 solution, the composition of which is the following: 



Mercuric chlorid 0-5 



Sodium sulphate 5-0 



Sodium chlorid 10 



Aq. dest 200.0 



