The relative number of red discs to the colorless cells is said to be, on the average, 350 to 1. This is true of the blood drawn from the fine vessels by puncture. While in the vessels the blood must contain a greater proportion of the colorless cells, for by the ordinary method of obtaining blood for examination, they do not flow out of the punctured capillaries as readily as the red discs, and many of them are said to become disintegrated very shortly after they are removed from the circulation. Although the number of red discs normally alters but little, on account of the constant changes occurring in the number of the white cells, the proportion of white to red varies much. It has been found to differ according to the observer, the situation, and other circumstances, as shown in the following table, which gives the number of red corpuscles to one colorless cell: -

Human Blood after death of the elements.

Fig. 97. Human Blood after death of the elements. The red corpuscles are seen in different positions showing their shape, some also in rolls. Only one white cell (w) is seen, misshapen and entangled in fibrin threads.

Observer's estimate of normal proportion :-

Red. White.

Welcker, . . ......

... 335-1

Moleschott, . ...

.... 357-1

In various parts of the circulation : -

Splenic vein, . .

60-1

Splenic artery, . .

2260-1

Hepatic vein, . .

170-1

Portal vein, . . .

..... 740-I

According to age or sex :-

Girls, . . .

....... 405-1

Boys, .... .......

226-1

Adult, .

....... 334-1

Old age, ... ...

....... 381-1

According to general conditions : -

Red. White.

When fasting

..... 7I6-I

After meal

347-1

During pregnancy

..... 28I-I

In a disease of the spleen and lymphatic glands called Leuco-cythemia there may appear to be nearly as many white cells as red discs. Here, however, the red discs are deficient, while the colorless cells are multiplied.