William F. Fox, Lt. Col. U. S. V., Regimental Losses in the American Civil War, 1861-1865: A Treatise on the extent and nature of the mortuary losses in the Union regiments, with full and exhaustive statistics compiled from the official records on file in the state military bureaus and at Washington

There are certain regiments which do not appear in the foregoing table, and yet they were regiments which had encountered an unusual amount of hard fighting. They had been in too many battles and sustained heavy losses in too many of them, to allow a surprising loss in any one. Notably among such were the Twentieth and Twenty-eighth Massachusetts, the Fourteenth Connecticut, the Ninth Maine, the Second New Hampshire, the Forty-fourth, Fifty-first, and Sixty-first New York, the Forty-fifth, Fifty-third, Eighty-first, and One Hundredth Pennsylvania, the Fifth Michigan, the Fifth and Sixth Wisconsin, the Twentieth and Twenty-seventh Indiana, the Fifteenth Ohio, and the Forty-second Illinois.

In these figures the mortally wounded are included with the killed, as the object is to state clearly the loss of life in each instance instead of the total casualties. The proportion of the wounded to the number killed or died of wounds is very near 2.5. This ratio is based on the figures, after the mortally wounded have been deducted from the wounded and added to the killed.

This ratio of 2.5 must not be confounded with the one representing the usual proportion of wounded to killed, as shown in statements of aggregate losses in battle. In such losses the proportion of wounded to the killed is about 4.8, the mortally wounded being always included with the wounded; for the casualty lists are made up at the close of the battle, and with the killed are included only those who died on the field. In all such statements — of killed, wounded, and missing — the mortally wounded are necessarily included with the wounded, and the word killed refers only to those who were killed outright, or died within a few hours.

The proportion of 4.8 is an average ratio as regards the aggregate of losses in battle, but is not a constant one. It varies somewhat, the proportion of killed increasing where the fighting is close and destructive, while in long range fighting the proportion of wounded increases.