562 SAMUEL H. HURWITZ 



portion of urobilin absorbed from the intestine may be variable, some 

 being destroyed and some resorbed by the portal blood, although unques- 

 tionable proof of this is lacking ( Hooper (c)) ; second, there is evidence 

 that some urobilin may be produced at times in the liver, and that liver 

 function may in part govern its formation (Whipple(fr)). It is therefore 

 important in a discussion of the influence of blood destruction on urobilin 

 excretion to bear in mind the probable hepatic origin of urobilin. 



In spite of these sources of error, however, estimations of the amount 

 of urobilin in the urine and feces give a fairly accurate index of the 

 degree of hemoglobin destruction ; especially if the quantity of urobilin in 

 the feces be compared in any instance with the normal. The figures so 

 obtained are of sufficient accuracy for clinical purposes. 



Another method which promises to give information of value in regard 

 to the rate of blood destruction has been described by Sellards and Minot. 

 They have found that it is possible to inject, without danger, concentrated 

 sterile solutions of hemoglobin into patients for the study of blood 

 destruction; and that such injections will cause hemoglobinuria in patients 

 showing evidences of increased blood destruction more frequently than in 

 normal controls. To a certain extent, this method yields results of quan- 

 titative value inasmuch as the amount of hemoglobin needed to induce 

 hemoglobinuria is directly proportional to the degree of blood destruction. 

 And it is further of interest that the tolerance to hemoglobin can be shown 

 to be low in conditions which are usually associated with increased elim- 

 ination of urobilin. The underlying basis of the two methods of study 

 is, however, quite different. Whereas, the urobilin output depends, in 

 part at least, upon the amount of blood-derived pigment excreted from 

 the body, hemoglobin tolerance depends upon the amount of pigment 

 which accumulates in the body. 



The Regulatory Influence of the Spleen in Blood Formation and De- 

 struction. The problem of the relation of the spleen to blood formation 

 and destruction has been the subject of numerous studies on patients and 

 on animals. A large amount of contradictory evidence has been gathered 

 which it is difficult to correlate. With regard to certain of the experi- 

 mental observations, however, there appears to be some uniformity of 

 opinion. 



Nearly all investigators attribute to the spleen a function in the 

 destruction of red cells; and some ascribe to it a part in red cell forma- 

 tion ; while some are inclined to the view that the spleen is concerned both 

 with the regeneration and the destruction of blood. An effort will be 

 made to analyze briefly the evidence for these opposing views. 



The conception that splenic function is essential for red cell forma- 

 tion is based largely on the fact that in fetal life erythrocytes are formed 

 in the spleen, and that under pathological conditions myeloid metaplasia 

 may occur in this organ. That this erythrogenetic function may in some 



