Читать книгу The Body at Work: A Treatise on the Principles of Physiology онлайн

58 страница из 88

Hæmoglobin is a substance which has the property of uniting with oxygen to form oxyhæmoglobin—a compound from which the oxygen is, again, very readily withdrawn. It is extremely soluble, but may be made to crystallize by adding alcohol to blood, after setting the hæmoglobin free from the corpuscles by freezing and thawing. From the blood of Man and most other animals it crystallizes in the form of rhombic prisms, whether in the oxidized (oxyhæmoglobin) or non-oxidized condition. The addition of oxygen does not affect its crystalline form; although crystalline, it is absolutely non-diffusible. This is due to the great size of its molecule, which is probably larger than that of any other substance which is capable of crystallizing.

The percentage composition of hæmoglobin conforms closely with that of albumin and other proteins, with this most important difference: it contains a definite proportion of iron—0·336 per cent. That the percentage of carbon, hydrogen, nitrogen, sulphur, and oxygen should agree with that commonly found in proteins is inevitable, since it may be split into a part which contains all the iron, hæmatin, and a proteid part resembling albumin; and the latter constitutes 96 per cent. of its weight.