4. Snap off the sealed end of the pipette with a pair of sterile forceps. 5. Compress the india-rubber teat, thrust the point of the pipette into the secretion; now relax the pressure on the teat and allow the pipette to fill. 6. Remove the point of the pipette from the secretion, allow the fluid to run a short distance up the capillary stem and seal the point of the pipette in the flame. (If using a pipette with a constriction below the plugged mouthpiece (Fig 13b), this portion of the pipette may also be sealed in the flame.) When ready to examine the morbid material snap off the sealed end of the pipette with sterile forceps and eject the contents of the pipette into a sterile capsule. The material can now be utilized for cover-slip preparations, cultivations and inoculation experiment. 3. _The peripheral blood_ should be examined from time to time for from this tissue is often obtained the fullest information as to the course and progress of an infection. a. The ~histological examination of the blood~ should be directed chiefly to observations on the number and kind of white cells; and since but few bacteriologists are at the same time expert comparative hæmatologists, some notes on the normal characters of the blood of the commoner laboratory animals, contrasted with those of man, are inserted for reference. These have been very kindly compiled for me by my friend and one time colleague Dr. Cecil Price Jones. COMPARATIVE HÆMOCYTOLOGY OF LABORATORY ANIMALS. -------------------------------------------------------------------- | Totals | Percentages |------------------------------------------------------------ Animal | | | Hb, |Lympho-|Large |Poly- |Eosin-| Mast |Red cells |White | per | cytes,|monos,|morph,| oph, |cells, | | cells|cent.| per | per | per | per | per | | | | cent. | cent.| cent.|cent. |cent. -------------------------------------------------------------------- Frog | 490,000| 8,000| 58 | 40 | 10.0 | 22.0 |15 | 13 Mouse | 8,700,000| 8,000| 78 | 60 | 21.5 | 17.0 | 1.4 | 0.1 Rat | 9,000,000| 9,000| 85 | 54 | 7.0 | 37.5 | 1.3 | 0.2 Guinea-| | | | | | | | pig | 5,700,000|10,000| 99 | 55 | 9.0 | 32.8 | 3.0 | 0.2 Rabbit | 6,000,000| 7,000| 70 | 50 | 2.0 | 46.0 | 0.6 | 1.4 Rhesus | 4,500,000|13,000| 77 | 43 | 5.0 | 50.0 | 1.3 | 0.7 Goat |14,600,000|15,000| 58 | 35 | 6.3 | 56.7 | 1.25 | 0.75 Fowl | 3,500,000|30,000| 100 | 49 | 3.0 | 42.0 | 1.0 | 5.0 Pigeon | 3,500,000|20,000| 101 | 43 | 9.0 | 43.0 | 3.0 | 2.0 -------------------------------------------------------------------- Man | | | | | | | | (adult)| 5,000,000| 7,500| 100 | 25 | 5.5 | 65 | 4.0 | 0.5 Normal | (4.5-5) | (7-9)|(95- |(20-30)| (4-8)|(55- |(3-5) |(0.5-2)