No one can write even a limited history of Ireland without mentioning the potato and the famine(s). Neither shall I ignore this both blessing and curse of the Irish race and how it effected the historic Donnellans. Although starvation was the symptom of the calamity, the disease(s) were the causes of at least half of the deaths in Ireland. Weakened by lack of food, the population fell into a malaise of idleness and slovenliness. This brought on the infestation of ticks and disease carrying vermin that knew no discrimination.

At first, the savior of the Irish peasantry because of its ability to support and feed a growing population, the potato became the bane of the Irish on more than one occasion. Crop failures occurred in 1740-41; no less than 14 of them between 1816 and 1842; and, of course, the great blight of 1845, 1846, and again in 1848. There were also a number of other regionally confined crop failures that occurred since the potatoes introduction to Ireland in the late 1500s.
Ireland was the first country in Europe where the potato became a major food source. Because it was abundant, and could feed so many people, it allowed the population to grow very quickly. Conversely, any failure in the crop could, and did, bring devastation.

As aforementioned, the disease brought on by the starvation took no prisoners. The vermin passed quicky from anyone coming in contact by simple transference from clothing of one to the body or clothing of another. It was that carried to all classes of people and, after infecting one, simply moved on to another host.
How did this effect the Donnellans ? Only clues exist to hint at its ominous presence.
In the Irish Memorials to the Dead, Volume III, No. 1, published in 1895, we find this sad entry on a graveyard stone in Kildare:

"John Donnellan died Apl ye 20th 1741 Aged 36.
Hannah Donnellan died May ye 10th 1736 Aged 2 years.
Tersesa Donnellan died March ye 16th 1737 Aged one year & a half.
Nehemiah Donnellan died August ye 13th 1739 aged one year.
Elizabeth Donnellan died July ye 16th 1741 Aged 2 years."

Once again, quoting from the same source:

"Above this inscription, carved in relief, is an ornamental shield with two coats-of-arms impaled, and a helmet and crest, as given below:

For Donnellan, - Argent, a tree eradicated vert, fructed or. The sinister impalement is: - A fess between three crosslets fitche (or three crosses potent fitche). If the former it may possibly be intended for the arms of the Gore family.
The above information on the coats was obtained from Sir Arthur Vicars (Ulster), as Burke's 'General Armory' did not give a Donnellan coat corresponding with those on the stone.

And yet, it is a simple matter to cross -check this with the entry in Ms. 467, Donnellan pedigree, and locate this family. The question - did the potato famine of 1740-41 have something to do with this tragedy ?