How is the temperature read in the clinical thermometer?

The temperature difference indicated between the two bigger marks is noted. Also, the number of divisions (shown by smaller marks) between these marks is noted. For e.g. the bigger mark reads 10 and the number of division is 5, then each division reads the value equal to 10/5 = 20. We note the value of the bigger mark that the mercury thread has crossed (which is 98 in the Fig.4 Example 1). Then the number of the division of the mercury thread has crossed is noted (3 in this case). Now, this value is multiplied by the value of one division (which is 0.2 in this case). Hence, the temperature reading is 98 + (32) = 98.6