We first find the absorbances of the unknown on the absorbance axis of the plot and then read the corresponding concentrations on the concentration axis. The lines leading from the cuvettes to the calibration curve show that the concentrations of arsenic in the two deer were 16 ppm and 22 ppm respectively. Arsenic in the kidney tissue of an animal is toxic at lev els above about 10 ppm, so it was probable that the deel were killed by ingesting an arsenic compound.