512 



ORGAN SYST 



formed 



Fig. 19-16. Complications may arise when an Rh positive 

 man marries an Rh negative woman, as indicated in 

 these figures. The explanation is given in the text. 



for some reason or other the blood of an 

 Rh positive and an Rh negative are mixed. 

 Under these conditions the protein contain- 

 ing the Rh factor acts hke a foreign protein 

 in the Rh negative person giving rise to the 

 anti-Rh antibody. If, then, at some subse- 

 quent period such a person receives another 

 transfusion of Rh positive blood, agglutina- 

 tion of the donor's red cells will occur be- 

 cause the anti-Rh is present in the recipi- 

 ent's serum (Fig. 19-15). Such clumped 



EMS OF MAN 



• 



blood cells will produce serious reactions 

 and even death. For this reason, before 

 blood tiansfusions are given, the Rh condi- 

 tion of the blood is determined and a his- 

 tory of any previous transfusions is impor- 

 tant. 



The Rh factor also explains the cause of 

 a disease of newly born infants called eryth- 

 roblastosis fetalis. This disease is respon- 

 sible for the death of a small percentage of 

 babies shortly after birth, and was hereto- 

 fore a complete mystery. It is now known 

 that the Rh positive factor is inherited as 

 a dominant, and the Rli negative factor 

 as a recessive. This means that it will ap- 

 pear in either half or all of the offspring of 

 an Rh positive father and an Rh negative 

 mother. When the developing fetus of this 

 combination inherits the Rh positive factor 

 from its father it is possible that trouble 

 will follow (Fig. 19-16). Normally the 

 blood of the mother does not come into 

 direct contact with the blood of the fetus, 

 but occasionally a very small number of red 

 cells apparently do get into the maternal 

 circulation, perhaps by the accidental break- 

 ing of small capillaries in the placenta. 

 Once Rh positive red cells get into the 

 mother's circulation, Rh antibody is pro- 

 duced. Since the antibody is present in the 

 serum, it can easily diffuse through into 

 the fetal circulation, causing damage to the 

 red cells of the developing fetus. Such a 

 child, when born, will be highly deficient 

 in red blood cells, which results in a severe 

 jaundice, and unless immediate treatment 

 is given will die. The child may be saved 

 by numerous blood transfusions during the 

 first few weeks of life. 



The situation is not as serious as it might 

 appear as attested by the small number of 

 babies born with this disease. This is owing, 

 perhaps, to the fact that not all cases of 

 pregnancy result in a mixing of the fetal 

 and maternal blood. Furthermore, not 

 enough antibody is generally produced to 

 cause trouble on the first pregnancy so the 

 condition does not usually show up until 



