The fluid pumped through the animals beginning one hour after their deaths is composed of equal parts of the animals’ blood and a cocktail of substances that mimic hemoglobin’s ability to carry oxygen ...

The animals’ blood—bright blue because it contains copper rather than iron like ours—is collected for one key reason: It clots in the presence of “endotoxins.” Endotoxins are shed when gram-negative ...

including prevention of accidental transmission through blood transfusion and organ transplant and large-scale screening to prevent the entry of diseased animals into the food supply.

ILAR News 31(4), 5–20 (1989). Luzzi, M. et al. Collecting blood from rodents: a discussion by the Laboratory Animal Refinement and Enrichment Forum. Anim. Technol. Welf. 4(2), 99–102 (2005).